CBSE Class 10 Physics Magnetic Effect of Electric Current Worksheet Set D

CBSE Class 10 Physics Magnetic Effect of Electric Current Worksheet Set D

MCQ Questions for NCERT Class 10 Science Magnetic Effects Of Electric Current 

Question. Three magnets A, B and C wire dipped one by one in a heap of iron filing. It shows the amount of the iron filling stucking to them: 

The Strength of these magnets will be:
(a) A > B > C
(b) A < B < C
(c) A = B = C
(d) A < B > C

Answer: A

Question. Which of the given options represents the correct pair?
(a) Right-hand thumb rule Direction of force
(b) Galvanometer Adjust current in circuit
(c) Earth wire Red colour
(d) MRI Magnetic Resonance Imaging

Answer: D

Question. If we place the magnetic compass near the north pole of the magnet, which pole of the needle will point towards it? 

(a) North pole
(b) South pole
(c) Keep deflecting
(d) None of these

Answer: B

Question. In the circuit shown below, what is direction of the current? 

(a) No current flowing
(b) Anti-clock wise
(c) Clock wise
(d) Data insufficient

Answer: C

Question. The strength of an electromagnet after the limit cannot be increased by increasing the current through the solenoid. What is the reason behind this phenomenon?
(a) Electrons start to corrode the solenoid.
(b) Voltage through the solenoid gradually starts to decrease.
(b) Resistance of the solenoid increases.
(d) Current flowing through the solenoid is saturated.

Answer: D

Question. A proton enters a magnetic field at right angle to it, as shown below. The direction of force acting on the proton will be:
(a) To the right
(b) To the left
(c) Out of the page
(d) Into the page

Answer: D

Question. The magnetic field strength of a solenoid can be increased by inserting:
(a) a wooden piece into it.
(b) an iron piece into it.
(b) a glass piece into it.
(d) paper roll into it.

Answer: B

Question. Rashita and her friends were decorating the class bulletin board.
She accidently dropped the box of stainless steel pins by mistake. She tried to collect the pins using a magnet. She could not succeed. Why?
(a) They are not using the magnet in right direction
(b) Steel pins are very heavy and cannot be lifted magnet
(c) Steel pins are very long
(d) Steel is not magnetic in nature

Answer: D

Question. Which of the following correctly describes the magnetic field near a long straight wire ?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(b) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.

Answer: D

Question. Which of the following combination is not correct?
(a) Electric Motor—Fleming's right hand rule
(b) Electric generator—Electromagnetic induction
(c) Earth wire—Green colour
(d) Compass Needle—Small Magnet

Answer: A

Question. If the current is passing through a straight conductor. then, the magnetic field lines around it forms a particular shape. That shape is:
(a) Straight lines
(b) Concentric circles
(c) Concentric ellipse
(d) Concentric parabolas

Answer: B

Question. A 3 pin mains plug is fitted to the cable for a 1 kW electric kettle to be used on a 250 V a.c. supply which of the following statements is not correct?
(a) The fuse should be filled in the live wire.
(b) A 13 A fuse is the most appropriate value to use.
(c) The neutral wire is coloured black.
(d) The green wire should be connected to the earth pin.

Answer: B

Question. In the given electric circuit, the device X is:
(a) Ammeter
(b) Resistance
(c) Galvanometer
(d) Voltmeter

Answer: C

Question. A rectangular loop carrying a current I is situated near a long straight wire such that the wire is parallel to one of the sides of the loop and is in plane of the loop. If steady current I is created in wire as shown in figure below, then the loop: 

(a) Rotate about an axis parallel to the wire
(b) Move towards the wire
(c) Move away from the wire or towards right
(d) Remains stationary

Answer: B

Question. The strength of magnetic field inside a long current carrying straight solenoid is:
(a) more at the ends than at the centre.
(b) minimum in the middle.
(c) uniform at all points.
(d) found to increase from one end to the other.

Answer: C

Question. The magnetic lines of force, inside a current carrying solenoid are:
(a) Along the axis and are parallel to each other
(b) Perpendicular to axis and equidistant from each other
(c) Circular and they do not intersect each other
(d) Circular at the ends but they are parallel to the axis inside the solenoid

Answer: A

Question. The core of electromagnet is made of:
(a) soft iron
(b) steel
(c) magnesium
(d) copper

Answer: A

Question. In the diagram shown below, what is the component A: 

(a) Solenoid
(b) Glass rod
(c) Magnetic material
(d) None of these

Answer: C

Question. Which of the following determine the direction of magnetic field due to a current carrying conductor?
(a) Faraday's laws of electromagnetic induction
(b) Fleming's left hand rule
(c) Lenz's law
(d) Maxwell's cork screw-rule

Answer: D

Question. Which of the following is not an example of the right hand thumb rule ?
(a) D.C. motor
(b) Solenoid
(c) A.C. generator
(d) Cartesian coordinate system

Answer: C

Important Questions for NCERT Class 10 Science Magnetic Effects of Electric Current

Very Short Answer Type Questions :

Question. Why does a current-carrying conductor experience a force when it is placed in a magnetic field?
Answer: A current-carrying conductor produces a magnetic field around it. This magnetic field interacts with the externally applied magnetic field and as a result the conductor experiences a force.

Question. What is the shape of a current-carrying conductor whose magnetic field pattern resembles that of a bar magnet ?
Answer: A solenoid

Question. How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire ?
Answer: Strength of magnetic field is directly proportional to the strength of current flowing in the wire.

Question. Define magnetism.
Answer: The property by virtue of which a magnet attracts certain metals such as iron, cobalt, nickel etc., is termed as magnetism.

Question. Define electromagnetic induction.
Answer: The production of electricity from magnetism is called electromagnetic induction.

Question. A stationary charge is placed in a magnetic field. Will it experience a force ? Give reason to justify your answer.
Answer: No, a magnetic field exerts a force only on a moving charge.

Question. What happens to the magnetic field lines due to a current carrying conductor when the current is reversed ?
Answer: The direction of magnetic field (and magnetic field lines) gets reversed on changing the direction of flow of current in a straight conductor.

Question. Name five main parts of a D.C. motor.
Answer: An electric motor is a device which converts the electrical energy into mechanical energy.
The five main parts of a D.C. motor are:
(a) Strong field magnet,
(b) Armature coil,
(c) Split ring or commutator,
(d) Carbon brushes, and
(e) Battery.

Question. Where will be the value of magnetic field maximum due to current-carrying circular conductor?
Answer: At the centre of current-carrying circular loop.

Question. State the conclusion that can be drawn from the observation that a current-carrying wire deflects a magnetic needle placed near it.
Answer: A magnetic field is produced around a current-carrying conductor.

Question. Why does a current-carrying conductor experience a force when it is placed in a magnetic field ?
Answer: A current-carrying conductor produces a magnetic field around it. This magnetic field interacts with the externally applied magnetic field and as a result the conductor experiences a force.

Question. State the conclusion that can be drawn from the observation that a current-carrying wire deflects a magnetic needle placed near it.

Answer: A magnetic field is produced around a current-carrying conductor.

 Long Answer Type Questions :

Question. (a) What is meant by a ‘magnetic field’?
(b) How is the direction of magnetic field at a point determined?
(c) Describe an activity to demonstrate the direction of the magnetic field generated around a current carrying conductor.
(d) What is the direction of magnetic field at the centre of a current carrying circular loop?
Answer : a. Magnetic field is the space around a magnet or a current carrying conductor in which its magnetic force can be experienced.
b. A magnetic compass is used to demonstrate the direction of the magnetic field generated around a current carrying conductor.
c. Fix a cardboard and insert a wire to pass through its centre normal to the plane of the card board. Sprinkle iron filings on card board uniformly. Pass the current in the wire. Tap the cardboard gently. You will find that iron filings align themselves in the concentric circles around the wire. These circles represents magnetic field lines around the conductor.
d. 

At the centre of circular loop, the magnetic field lines are straight.

Question. (a) What is the function of an earth wire in electrical instruments? Why is it necessary to earth the metallic electric appliances?
(b) Explain what is short-circuiting and overloading in an electric supply.
(c) What is the usual capacity of the fuse wire in the line to feed:
(i) lights and fans?
(ii) appliances of 2 kW or more power?
Answer : (a) We can get an electric shock on touching a faulty appliance, caused by the leakage of current from the appliance. Earthing provides a safety measure against the electric shock caused by the leakage of current. Earth wire brings this leakage current to the ground by a earth wire and we remains safe.
(b) Short circuiting takes place when a live wire and neutral wire come in contact with each other due to damage of insulation of these wires. Due to short circuiting, resistance of the circuit becomes minimum and a very high current is passed through the circuit which produces spark and heat and may lead a fire in the house. Overloading when the amount of current flowing through the circuit exceeds the rating of the protective devices it is said that circuit is overloaded. It is a situation in which many electrical appliances are connected in a single socket. It will draw more current, may lead the burst of fire in building.
(c) (i) Bulbs, fans etc. – 5A, (ii) Heater – Micro-oven, Electric iron – 15A

Question. Describe in short an activity to:
a. demonstrate the pattern of magnetic field lines around a straight current carrying conductor, and 
b. find the direction of magnetic field produced for a given direction of current in the conductor. Name and state the rule to find the direction of magnetic field associated with a current carrying conductor. Apply this rule to determine the direction of the magnetic field inside and outside a current carrying circular loop lying horizontally on a table. Assume that the current through the loop is anticlockwise.
Answer : (a) Fix a cardboard and pass through its centre a thick copper wire AB connected with a cell of 12 V through a rheostat, an ammeter and plug key as shown in figure. Sprinkle the iron filings uniformly on the cardboard. Plug in the key, tap the cardboard gently a number of times. Iron filings align themselves in a pattern of concentric circles around the copper wire, which represents the magnetic field lines.

If the direction of current is reversed the direction of magnetic field is also reversed. The direction of magnetic field can be found by using Ampere’s right hand thumb rule. According to it, if we hold a straight conductor in our right hand such that thumb points the direction of current in the conductor

Question. (a) State Fleming’s left hand rule.
(b) Write the principle of working of an electric motor.
(c) Explain the function of the following parts of an electric motor.
(i) Armature (ii) Brushes (iii) Split ring
Answer : (a) Fleming’s left hand rule state that if the thumb, forefinger and middle finger are stretched perpendicular to each other in such a way that forefinger indicates the direction of magnetic field, middle finger indicate the direction of current in the conductor then thumb will indicate the direction of force on the conductor.
(b) The principle of electric motor is that when a current carrying coil is placed in a magnetic field it experiences a torque and if the coil is allowed it rotates in the magnetic field.
(c) Function of the parts of an electric motor :
(1) Armature: Armature is a large number of turns of the coil on soft iron core which rotates in magnetic field.
(2) Brushes: They allow current to pass from external source to armature.
(3) Split rings: Split rings are of copper, splits into two halves and make a connection between armature and brushes.

Question. (a) Describe an activity to show the pattern of magnetic field fines of a bar magnet, with the help of a cardboard piece and iron filings.
(b) Compare the field of a bar magnet with that of a solenoid with the help of figure.
Answer : (a) Fix a white paper sheet on a drawing board with the help of copper pins. Keep a bar magnet in the centre of the paper and sprinkle some iron filings uniformly around the bar magnet. Tap the board gently. Iron filings arrange themselves in a pattern as shown in figure. These iron filings near the bar magnet align themselves along the magnetic field lines.

(b) A current carrying solenoid behaves as a bar magnet one end of the solenoid behaves like a N pole and another end as S pole like two poles in bar magnet, so the field lines of a solenoid and bar magnet appear same in many ways:
(i) Magnetic lines of force inside the body is strong and uniform.
(ii) In both the cases stronger field exists at the poles compared to the middle part.
Dissimilarities
(i) In bar magnet, the poles are not exactly at the ends of the magnet, in solenoid poles can be considered to be lying at the edges.
(ii) In bar magnet, magnetism is permanent but in solenoid it exists only till there is a current in solenoid.

Question. (a) Explain what is the difference between direct current and alternating current? Write one important advantage of using alternating current.
(b) An air conditioner of 2 kW is used in an electric circuit having a fuse of 10 A rating. If the potential difference of the supply is 220 V, will the fuse be able to withstand, when the air conditioner is switched on? Justify your answer.
Answer : (a) Direct current is a unidirectional current with constant magnitude. Alternating current is a current which change its magnitude and direction after a fixed period. AC voltage can be increased or decreased. Where is dc voltage cannot be increased or decreased. AC can be transmitted to long distances with lesser power loss.
(b) Given P = 2 kW and V = 200 volt,
Power,        P = VI ⇒ I = P/V
                 I = 2000/220 = 9.09 A
The rating of the fuse wire is 10 A which is greater than current drawn by air conditioner so when air conditioner is switched on, fuse will not blow off.

Question. What is a solenoid? Sketch magnetic field lines produced around a current carrying solenoid. Mark the region where field is uniform. Compare its field with that of a bar magnet.
Answer : A solenoid is a large number of insulated turns of the copper wire in the shape of helix (or cylinder). The patterns of the magnetic field lines around a current carrying solenoid is as given in figure. At the centre of the solenoid the magnetic field is uniform and magnetic field lines are parallel.
Similarities:
In both the cases of a current carrying solenoid and bar magnet the magnetic lines of forces inside the body is strong and uniform. In both the cases there exists stronger magnetic field at the poles compared to the middle parts.
Dissimilarities:
(i) The poles in a bar magnet do not exist at the extreme ends of the magnet whereas in solenoid the poles can be considered to be lying at the edge.

(ii) In a bar magnet, magnetism is retained naturally, but in solenoid magnetism is there so long current flows through it.

Question. (a) State the function of ‘a fuse’ in an electric circuit. How is it connected in the domestic circuit?
(b) An electric fuse of rating 3A is connected in a circuit in which an electric iron of power 1.5 kilo watt is connected which operates at 220 V. What would happen? Explain.
Answer : (a) Fuse is a safety device to prevent the damage of electrical devices from short circuit or overloading. A fuse is connected in series with the circuit.
(b) Given Power P = 1.5 kW = 1500 Watt and V = 220 Volts.
Power P = VI ⇒ I = P/V = 1500/220 = 6.8 A
The rating of fuse is 3A which is lesser the current drawn by electric iron 6.8 A. So fuse wire will be blown.

Question. (a) Draw magnetic field lines of a bar magnet. “Two magnetic field lines never intersect each other”. Why?
(b) An electric oven of 1.5 kW is operated in a domestic circuit (220 V) that has a current rating of 5 A. What result do you expect in this case?
Explain.
Answer : (a) Magnetic field lines around a bar magnet. 

If the two magnetic field lines would intersect with each other than at that point there will be two different directions of magnetic field which is not possible.
(b) Given Power P = 1.5 kW = 1500 Watt and V = 220 Volts.
Current drawn I = (P/V) = (1500/220)A
                      I = 7 A (approx).
As the current drawn by the oven is 7 A which is larger than the rating of the fuse (5A) so fuse will blow off and circuit will be broken.

Question. (a) Explain any three properties of magnetic field lines.
(b) Give two uses of magnetic compass.
Answer : (a) Properties of magnetic field lines:
1. Magnetic field lines emerge from N pole and merge at S pole outside a bar magnet and travel from S pole to N pole inside the magnet.
2. These are continuous and closed curves.
3. Two field lines never intersect each other.
(b) Uses of magnetic compass :
1. In navigation it is used to find direction.
2. It is used to detect the magnetic field.
3. It can be used to test whether a substance is magnetic or not.

Question. (a) Describe an activity to determine the direction of magnetic field produced by a current carrying straight conductor. Also show that the direction of the magnetic field is reversed on reversing the direction of current.
(b) An a -particle, (which is a positively charged particle) benters, a uniform magnetic field at right angles to it as shown below. Stating the relevant principle explain in which direction will this a-particle moves?

Answer : (a) Fix a cardboard and pass a straight wire through a hole in cardboard and connect the two ends of the wire with a cell through a rheostat and key with a cell. Sprinkle iron filings uniformly on the card board. Pass the current in the wire and gently tap the card board. You would find that iron filings align themselves in concentric circles around the copper wire which represents the magnetic field around the current carrying conductor. The direction of magnetic field changes on reversing the direction of current.
(b) According to Fleming’s left hand rule the force on the oc-particle will be inwards perpendicular to the plane of paper, so \-particle will move in the direction of force.

Question. Explain the meanings of the words “electromagnetic” and “induction” in the term electromagnetic induction. List three factors on which the value of induced current produced in a circuit depends. Name and state the rule used to determine the direction of induced current. State one practical application of this phenomenon in everyday life.
Answer : The word electromagnetic means that an electric potential dipole is being produced in a coil due to change in magnetic field. The word induction means that the current has been induced. The value of induced current produced in a circuit depends on the following factors:
a. number of turns in given coil 
b. area of each turn in coil
c. rate of change of magnetic field.
The rule is Fleming’s right hand rule. Stretch the thumb, forefinger and middle finger of righthand perpendicular to each other that forefinger indicates the direction of magnetic field, thumb gives the direction of motion (or force) of the conductor, then middle finger will point the direction of induced current.
Application: AC generator or DC generator.

Question. (a) Which effect of the electric current is utilised in the working of an electrical fuse?
(b) A fuse is connected in series or in parallel in household circuit?
(c) Draw a schematic labelled diagram of a domestic circuit which has a provision of a main fuse, meter, one light bulb and a switch socket. 
Answer : a. Heating effect of current b. In series in the household circuit c.

Question. (a) An electric current is passed in a horizontal copper wire from east to west. Explain your observations  when a compass needle is placed (i) below this wire, (ii) above the wire. Draw inference from your observations.
(b) List the factors on which the strength of the magnetic field due to a straight conductor carrying current depend. How should these be changed to decrease magnetic field at a point?
Answer : (a) The direction of deflection of a magnetic compass needle depends upon the direction of the magnetic field at that point. The direction of the magnetic field due to a current carrying wire is given by the right hand screw rule. The direction of magnetic field below and above the wire is opposite so deflection in compass needle changes as well i.e, the deflection is reverse direction.
(b) The factors affecting strength of the magnetic field due to a straight wire carrying current:
1. magnitude of current in the wire ∝ I
2- distance of the point from the wire ∝ 1/I
By decreasing current or increasing the distance of the point from the wire, strength of magnetic field also decreases.

Question. (a) Draw a schematic labelled diagram of a domestic wiring circuit which includes (i) a main fuse (ii) a power meter (iii) one light point and (iv) a power plug.
(b) Why is it necessary to connect an earth wire to electric appliances having metallic covers?
Answer : a.

b. The earth wire carry current due to any leakage or defective electric appliance to the earth keeping human beings safe preventing from any electric shock.
c. Properties of magnetic field lines
(i) They emerge from the north pole and merge at south pole of a bar magnet.
(ii) They do not intersect with each other.
(iii) They emerge and merge normal to the surface of magnet

Question. (a) Describe an experiment with a diagram to show that force is exerted on a current carrying conductor when placed perpendicular in a magnetic field.
(b) How will this force change if current in the conductor is increased?
(c) Name a device that uses the above principle.
Answer : a. Take a small metal rod AB and suspend it from a stand with the help of two connected wire. Put the rod in between the horse shoe magnet in such a way that rod remains in between the two poles. Pass the current in the rod through the two wires. You would find that the rod is deflected towards the left. Now reverse the direction of current the rod is deflected in opposite direction. This shows that a force is experienced by a current carrying conductor in magnetic field.
b. If the current in the conductor is increased then more force will act on the rod, and get more deflected.
c. Electric motor.

Question. Answer the following questions:
a. What is the direction of magnetic field lines outside a bar-magnet?
b. Why two magnetic field lines cannot intersect each other?
c. What is indicated by crowding of magnetic field lines in a given region?
d. What is the frequency of ac in India?
e. State one advantage of ac over dc.
Answer : a. From N pole to S pole
b. If two magnetic field lines would intersect each other then at the point of intersection there would be two different directions of magnetic field which is not possible.
c. Magnetic field strength is more in that region.
d. 50 cycles per sec (c/s) or Hz.
e. AC can be step up for transmission over a longer distances with less power loss.

Question. (a) Name two electrical appliances of daily use in which electric motor is used.
(b) Name and state the principle on which an electric motor works.
Answer : (a) Drill machine, fan, grinder
(b) An electric motor works on the Fleming’s left hand rule. When a current carrying coil is placed in a magnetic field it experience a torque due to which it rotates.
Fleming’s left hand rule-stretch left hand, thumb, forefinger and middle finger perpendicular to each other in such a way that forefinger indicates the direction of magnetic field, middle finger indicates the direction of current in the conductor then thumb will point the direction of force on the conductor,

Question. (a) What is an electromagnet? What does it consist of?
(b) Name one material in each case which is used to make a : (i) permanent magnet (ii) temporary magnet.
(c) Describe an activity to show how you can make an electromagnet in your school laboratory.
Answer : a. A soft metal core made into a magnet by the passage of electric current through a coil surrounding it. It consists a soft iron core or its alloy and a solenoid conductor coil around the core.
b. (i) To make a permanent magnet alloy Alnico is used. (ii) Soft iron is used to make temporary magnet.
c. Take a long nail and put it into a solenoid of insulated copper wire. Pass the strong current in the solenoid the nail inside the solenoid becomes magnetised. This is called electromagnet.

Question. (a) The given figure shows a domestic electric circuit. Study this circuit carefully. List any two errors in the circuit and justify your answer.

(b) Give one difference between the wires used in the element of an electric heater and in a fuse.
(c) List two advantages of parallel connection over series connection.
Answer : (a) Errors in the circuit
(i) Fuse wire is connected in neutral wire (N) where as it must be connected in live wire (L).
(ii) Circuit of bulb B2 is incomplete. 
(b) Element of electric heater has high resistance and high melting point whereas a fuse wire has high resistance and low melting point.
(c) Advantages of parallel connection over series connection.
(i) In parallel combination if one appliance fails to work others keep working.
(ii) Potential difference across each appliance remains same.

Question. (a) When do we state that an electrical appliance is earthed? Mention the function of earth wire in electric lines. Why is it necessary to earth the electric appliances having metallic body?
(b) Explain what is short circuiting and overloading in an electric supply.
Answer : (a) When metal body of an electric appliance is connected to a wire which is connected to a metal plate buried deep inside the earth is said to be electrically earthed.
(b) If due to damaged insulation, live wire and neutral wire come in contact with each other then it is said to be short circuiting overloading. A circuit over load occurs when the amount of current flowing through the circuit exceeds the rating of the protective device. Every electric circuit in a wiring system must be protected against overloading. It happens when too many electric appliances are connected into a single socket.

Question. (a) Define electromagnetic induction.
(b) Two coils P and S are wound over the same iron core. Coil P is connected to battery and key the coil S is connected to galvanometer. Draw a suitable diagram of this arrangement and write your observations when:
(i) current in the coil P is started by closing the key.
(ii) current continues to flow in coil P.
(iii) current in coil P is stopped by removing the key.
Explain the reason for such observations.
Answer : a. The phenomenon by producing a current in a coil by changing magnetic field associated with it or by changing a current in the neighbouring coil is called electromagnetic induction. Current so produced is called induced current.
b. (i) When key K is closed due to increasing current a magnetic field is produced which is changing. In this changing magnetic field coils is kept so an induced current flow through it, so galvanometer shows a deflection.
(ii) After some time current reaches maximum and becomes constant in P coil. There is no change in current so there is no change in magnetic field associated with coil S and hence no induced current in coil S. Deflection in galvanometer becomes zero.

(iii) Current becomes zero from maximum in coil P and hence galvanometer shows a deflection but now it is in opposite direction.

Question. (a) Write the values of the following physical quantities in connection with domestic power supply in our country: (i) potential difference between live wire and neutral wire. (ii) frequency of ac. 
(b) Explain the role of the following as safety measure in domestic electric appliance/circuits: (i) earth wire (ii) fuse.
Answer : (a) (i) 220 V, (ii) 50 Hz
(b) Safety measure in electric appliance/circuits: 
(i) Earth wire is a safety device to protect us from electric shock due to leakage of current or faulty electric appliances. An earth wire is a thick copper wire connected to a metal plate buried deep in the earth. The metallic body of the electric appliance is connected to the earth wire, it provides a low resistance conducting path and leaked current goes to deep in the earth and human beings do not get a fatal electric shock.
(ii) Fuse: It is also a safety device. It is a wire of an alloy with low melting point. If a current greater than a particular values flows in the circuit it will melt and circuit is broken and stops power supply in the circuit.

Question. (a) A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is:
(i) pushed into the coil with its north pole entering first?
(ii) withdrawn from inside the coil?
(iii) held stationary inside the coil?
(b) Name the above phenomenon and mention the name of the scientist who discovered it. State the law that relates the direction of current in the coil with the direction of motion of the magnet.
Answer : a. (i) Galvanometer gives a deflection
(ii) Again galvanometer gives a deflection but in opposite direction.
(iii) No current is induced in the coil so no deflection in the galvanometer.
b. Electromagnetic induction (EMI):
Faraday discovered it. Fleming’s right hand rule gives the direction of induced current in the coil. If we stretch right hand thumb, forefinger and middle finger perpendicular to each other in such a way that thumb gives the direction of motion of the conductor, forefinger gives the direction of magnetic field then middle finger will give the direction of current induced in the conductor.

Question. Two coils C₁ and C₂ are wrapped around a nonconducting cylinder. Coil C₁ is connected to a battery and key and C₂ with galvanometer G. On pressing the key (K), current starts flowing in the coil C₁ State your observation in the galvanometer.

a. What key K is pressed on.
b. When current in the coil C₁ is switched off.
c. When the current is passed continuously through coil C₁.
d. Name and state the phenomenon responsible for the above observation. Write the name of the rule that is used to determine the direction of current produced in the phenomena.
Answer : a. Induced current in coil C₂ is produced so galvanometer shows a deflection.
b. Again galvanometer shows a deflection but in opposite direction to the previous one.
c. There will be no deflection in galvanometer.
d. This phenomenon is called electromagnetic induction. The phenomenon in which a changing magnetic field in a coil induces a current in another coil kept near it. Fleming’s right hand rule is used to find the direction of induced current.

ORAL QUESTIONS

1. a) What are magnets?

    b) What are natural magnets?

    c) What is the meaning of the word lodestone?

    d) What is the origin of the word magnetism?

2. a) State the law of magnetic poles.

   b) What is the surer test of magnetism?

   c) What happens if we break a magnet into two pieces?

   d) Is it possible to obtain isolated north and south poles?

3. a) What is magnetic line of force?

   b) Can two magnetic lines of force intersect? Give reason.

   c) Magnetic lines of force are endless. Comment.

  d) How do the field lines of the regions of strong field different from those of weak  field?

4. a) What is a solenoid?

   b) Is the magnetic field of a solenoid similar to that of a bar magnet?

   c) State the two factors by which the strength of magnetic field inside a solenoid can be increased.

   d) How will you determine the direction of the magnetic field due to a current –carrying solenoid?

5. a) What is an electromagnet?

   b) What is the effect of placing an iron core in a solenoid?

  c) What type of core should be used inside a solenoid to make an electromagnet?

  d) Give two advantages of electromagnets.

wws

1. What important observation did Oersted make in his experiments with current carrying conductors?

2. How can you locate a current – carrying wire concealed in a wall?

3. A freely suspended magnet always points along north – south direction. Why?

4. What type of core should be used inside a solenoid to make an electromagnet?

5. Name the SI unit of magnetic field.

6. What is the principle of an electric motor?

7. A generator converts energy from one form to another. What is this energy conversion?

8. Which wire (live, neutral or earth) goes through the switch?

9. Are different appliances connected in series or parallel in a house?

10. What is the colour convention for live, neutral and earth wires?

PUZZLE

=> Across

1. A method preventing electric shock due to touching of live wire with the metallic body of an appliance.

2. A device to convert electrical energy into mechanical energy.

3. A device to convert mechanical energy into electrical energy.

4. SI unit of magnetic field.

↓ Down

5. A material having attractive and directive properties.

A temporary magnet.     A device to protect a circuit from overloading.

ANSWERS-MAGNETISM