CBSE Class 10 Physics Electricity Worksheet Set D

 

Short Answer Type Questions : 

Question. What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.
Answer : Resistivity quantifies the property of a conducting material due to which it opposes the flow of current. Electrical resistivity is also known as resistivity, specific electrical resistance, or volume resistivity.
The the SI unit of resistivity is Ωm.

Take an ammeter, a cell, plug key, nichrome wire, wires of other metals, etc. Complete the circuit; as shown in the diagram.
Use nichrome wire of a particular length in the first case. Replace this with a nichrome wire of different length. Repeat the step with a third nichrome wire of different thickness. Finally, use a copper wire instead of nichrome wire.
Now replace the wire by a thicker nichrome wire, of the same length l [marked (3)]. A thicker wire has a larger cross-sectional area. Again note down the current through the circuit.
It is observed that resistance varies when the conducting material is changed. Resistance of the nichrome wire increases when its length is increased. Resistance of nichrome wire decreases when its thickness, i.e. area of cross-section is increased.
It can be said that resistance depends on the material, length and thickness of the conducting wire.

Question. A child has drawn the electric circuit to study ohm’s law as shown in following figure. His/Her teacher told that the circuit diagram needs correction. Study the circuit diagram and redraw it after making all corrections
Answer : The ammeter is connected in parallel and voltmeter is connected in series. While voltmeter is always connected in parallel in a circuit. Thus, the correct diagram is as follows.

Question. Should the resistance of an ammeter be low or high? Give reason.
Answer : Ideally the resistance of an ammeter should be zero, but it is not possible, therefore, resistance of an ammeter is almost negligible. If it is high or low, it will affect the electric current flowing through the circuit.

Question. B1, B2 and B3 are three identical bulbs connected as shown in this figure. When all the three bulbs glow, a current of 3A is recorded by the ammeter A.

(i) What happens to the glow of the other two bulbs when the bulb B1 gets fused?
(ii) What happens to the reading of A1, A2, A3 and A when the bulb B2 gets fused?
Answer : (i) Because there is no division of voltage in parallel circuit, thus glow of other two bulbs remain same.
(ii) Since, the total electric current is equal to the sum of electric current through each of the electrical components.
As all the three bulbs are identical, thus electric current draws from each of the individual bulb will be same.
The electric current through the electric circuit is equal to 3A when all the three bubs are functioning.
Thus, after getting fuse of B2, the total electric current through the circuit will be equal to 2A.
Therefore,
A will show 2A
A1 will show 1A
And A3 will show 1A

Question. How will you conclude that the same potential difference (voltage) exists across three resistors connected in a parallel arrangement to a battery?
Answer : Take three resistors R1, R2 and R3, a battery, an ammeter, a voltmeter and some wires. Complete the circuit; as shown in the diagram.

Measure potential difference when all the three resistors are connected in parallel.
Remove one of the resistors and measure the potential difference for remaining two resistors in parallel.
Remove the second resistor and measure the potential difference for the remaining resistor.
It is observed that the voltmeter shows same reading in all these conditions. This shows, that same potential difference exists across three resistors which are connected in parallel combination.

Question. Why is parallel arrangement used in domestic wiring?
Answer : Parallel arrangement used in domestic connection because:
There is no division of voltage among the electrical component, thus all works in better way.
Individual electrical components can be switched off or on without disturbing other.
Any other electrical component does not affected because of breaking down of any one.

Question. How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?
Answer : Take three resistors R1, R2 and R3, a battery, an ammeter, a voltmeter and some wires. Complete the circuit; as shown in the diagram.

Measure the electric current, using the ammeter as shown in the circuit diagram.
Now, connect the ammeter between R1 and R2 and measure the electric current.
Now, connect the ammeter between R2 and R3 and measure the electric current.
It is observed that the ammeter reading is same in all the three cases. This shows, that the same current flows through every part of a circuit in which resistances are connected in series.

Question. Draw a circuit diagram of an electric circuit containing a cell, a key, an ammeter, a resistor of 2 Ω in series with a combination of two resistors (4 Ω each) in parallel and a voltmeter across the parallel combination. Will the potential difference across the 2 Ω resistor be the same as that across the parallel combination of 4Ω resistors? Give reason.
Answer :

The total effective resistance because of the parallel connection of two resistors of 4Ω:
Let the total effective resistance because of parallel connection = R
Thus,1R = 14Ω + 14Ω = 24Ω = 12Ω 1R = 14Ω + 14Ω = 24Ω = 12Ω
Therefore, R = 2Ω R = 2Ω
The potential difference divided in the electric circuit when resistors are connected in series. In the given condition, the total effective resistance of the parallel connection is equal to 2Ω. Therefore two resistors of 2Ω each are connected in series.
Therefore, the potential difference across the 2Ω resistor be the same as that across the parallel combination of 4Ω resistor.

Long Answer Type Questions :

Question. Find out the following in the electric circuit given in following figure.

(a) Effective resistance of two 8 Ω resistors in the combination
(b) Current flowing through 4 Ω resistor
(c) Potential difference across 4 Ω resistance
(d) Power dissipated in 4 Ω resistor
(e) Difference in ammeter readings, if any.
Answer : (a) Let the total effective resistance in the combination = R
Therefore, 1R = 18Ω + 18Ω = 1 + 18Ω 1R = 18Ω + 18Ω = 1 + 18Ω = 28Ω = 14Ω = 28Ω = 14Ω
Thus, R = 4Ω R = 4Ω
Therefore, effective resistance = 4Ω
(b) Given, potential difference through the circuit, V = 8V
The total effective resistance of the circuit, R = resistance in series + effective resistance in parallel combination
⇒ R = 4Ω + 4Ω = 8Ω
Thus, electric current,I through the circuit = VR = VR
⇒ I = 8V 8Ω = 1 AI = 8V 8Ω = 1A
Since, there is no division of electric current in series combination,
thus, electric current through the 4Ω resistor = 1A
(c) Since there is no division of electric current, in the case of series connection.
Thus, electric current through the 4Ω resistor = 1A
Since, potential difference,V across the 4Ω resistor=IR
Therefore,V = 1A × 4Ω = 4V
(d) Electric current, I = 1A
Potential difference, through 4Ω resistor = 4V
Thus, power, P = V x I
⇒ P = 4V x 1A = 4 watt
Thus, power dissipated in 4Ω resistor = 4W
(e) Since resistors are connected in series, thus there is no difference in ammeter readings

 

1. a) Why is electricity more useful than other forms of energy?

   b) How is static electricity different from current electricity?

   c) What are conductors? Give examples.

   d) What are insulators? Give examples.

2. a) What constitutes an electric current?

   b) Name the SI unit of electric charge.

   c) Which is bigger – c coulomb of charge or a charge of an electron?

   d) How much is the charge on an electron? Can a charge less than this value exist?

  e) What is the number of electrons constituting one coulomb of charge?

3. a) Define electric current.

    b) Name the SI unit of current.

    c) Define one ampere.

    d) Is electric current a scalar of vector quantity?

4. a) What does an electric circuit mean?

   b) When does the current flow in an electric circuit?

   c) How can the current be kept continuous in a conductor?

   d) Which particles constitute current in a metallic conductor?

5. a) Define potential difference.

   b) Name the SI unit of potential difference.

   c) What is meant by saying that a potential difference between two points in 1volt?

   d) What is the relationship between work done, potential difference and charge moved?

ORAL QUESTIONS

1. Which unit is equivalent of joule / coulomb?

2. How does the resistance of a wire depend on its length?

3. How does the resistance of a wire depend on its area of cross – section?

4. When are resistors said to be connected in series?

5. When are resistors said to be connected in parallel?

6. Why is tungsten suitable for making the filament of a bulb?

7. Why is tungsten not used as a fuse wire?

8. Alloys are preferred over metals for making the heating elements of heaters. Why?

9. How is the direction of electric current related to the direction of flow of electrons in a wire?

10. Should the heating element of an electric iron be made of iron, silver or nichrome wire?

QUIZ – WHO AM I

1. I am equal to the charge carried by 6.25 x 1018 electrons.

2. I am the rate of flow of charge through any section of a conductor.

3. I am same as coulomb/second.

4. I am closed path along which electric charges can flow.

5. I am equal to the work done per unit charge from point to another.

6. I am same as joule/coulomb.

7. I oppose the flow of charges through any conductor.

8. I am same as volt/ampere.

9. I relate potential difference with current for a given resistance.

10. I am used to measure potential difference between two points of a circuit.

Across                                                                                                                                                                       Down

7. Unit of electrical power, named after the Scottish inventor of the steam engine                       1. Elementary particle that carries a positive charge

8. a rotating machine that transforms electrical energy into mechanical energy                           2. Electromagnetic radiation in the wavelength

9. The kind of electricity you create by rubbing a balloon on your head                                            range including infrared, visible, ultraviolet, and X-rays

13. Atom or group of atoms that carries a positive or negative electric charge as a result            3. Device for making, breaking, or changing the

    of having lost or gained one or more electrons                                                                               connections in an electrical circuit

14. Emission of radiant energy in the form of waves or particles                                                  4. Flash produced by a discharge of atmospheric electricity

15. It transmits electricity, like copper                                                                                            5. Complete path of an electric current including

16. Opposition to the passage of an electric current                                                                          the source of electric energy

19. Elementary particle consisting of a charge of negative electricity                                          6. Inventor of the electric light bulb

20. Smallest particle of an element that can exist either                                                             10. Force acting on particles of matter, tending to draw them together

      alone or in combination                                                                                                         11. Electrical charge with more protons than electrons

21. Uncharged elementary particle                                                                                             12. Electrical charge with more electrons than protons                                                                  

22. Electric potential or potential difference                                                                              15. Electrical flow through a conductor                                                                        

                                                                                                                                                   17. Definite quantity of electricity

                                                                                                                                                   18. Unit of electrical resistance

SUGGESTED PROJECT / ACTIVITIES

1. Make a study of electrical conductivity of different materials or components.
2. Study the factors on which the resistance of a conducting wire depends.
3. Show experimentally that current thought each resistor when connected in series is same.

SEMINAR

1. Why in domestic electric circuits, electric appliances are connected in parallel and not it series? Explain.
2. Precautions to be taken while handling electrical appliances.
3. Working of lightning conductor in tall buildings.
4. Describe the practical applications of heating effect of current.

ACTION PLAN
From newspapers find out the accidents caused by electricity of lightening and suggest some preventions to be taken.

HAVE FUN THROUGH RESEARCH
Surf the internet and write the life story of the great scientist Thomas Alva Edison who invented electric bulb.

CBSE Class 10 Physics Chapter 12 Electricity MCQs

Question. What is immaterial for an electric fuse wire?
(a) Its specific resistance
(b) Its radius
(c) Its length
(d) Current flowing through it
Answer. C

Question. The amount of heat produced in a conductor is
(a) directly proportional to the current flowing through it
(b) inversely proportional to the current flowing through it
(c) directly proportional to the square of the current flowing through it
(d) inversely proportional to the square of current flowing through it.
Answer. C

Question. Specific resistance is numerically equal to the resistance offered by
(a) 1 cm length of a conductor
(b) a conductor of unit cross-section
(c) 1 cm length of conductor of 1 cm2 of crosssection
Answer. C

Question. Calculate the length of aluminium wire of area of cross-section 1 mm2 whose resistance is 1.56 × 10^–2 W. Given, resistivity of aluminium is 2.6 × 10^–8 W m.
(a) 60 mm
(b) 60 cm
(c) 60 m
(d) 6 m
Answer. B

Question. If current through a resistance is increased by 100%, simultaneously reducing resistance value to 25%, the new power dissipated will be
(a) same
(b) increased by 100%
(c) decreased by 400%
(d) increased by 400%.
Answer. A

Question. Suppose five resistances, each of 10 ohm, are provided to you. You are free to get the desired value by combining them. The desired value will lie in between
(a) 2 ohm to 50 ohm
(b) 20 ohm to 40 ohm
(c) 12 ohm to 50 ohm
(d) 10 ohm to 60 ohm
Answer. A

Question. A current of 4.8 A is flowing in a conductor.
The number of electrons passing per second through the conductor will be
(a) 3 × 10²⁰
(b) 76.8 × 10²⁰
(c) 7.68 × 10^–19
(d) 3 × 10¹⁹
Answer. D

Question. In order to distribute a high potential, we connect a number of resistors
(a) in series
(b) in parallel
(c) some in series and some in parallel
(d) It is not possible to distribute potential.
Answer. A

 

CBSE Class 10 Physics Chapter 12 Electricity Case Based MCQs

Case I : Read the passage given below and answer the following questions.

Two or more resistances are connected in series or in parallel or both, depending upon whether we want to increase or decrease the circuit resistance.

The two or more resistances are said to be connected in series if the current flowing through each resistor is same. The equivalent resistance in the series combination is given by
R_S = R₁ + R₂ + R₃

Question. When three resistors are connected in series with a battery of voltage V and voltage drop across resistors is V₁, V₂ and V₃, which of the relation is correct?
(a) V = V₁ = V₂ = V₃
(b) V = V₁ + V₂ + V₃
(c) V₁ + V₂ + V3 = 3V
(d) V > V₁ + V₂ + V₃
Answer. B

Question. When the three resistors each of resistance R ohm, connected in series, the equivalent resistance is
(a) R/2
(b) > R
(c) < R/2
(d) < R
Answer. B

Question. There is a wire of length 20 cm and having resistance 20 W cut into 4 equal pieces and then joined in series. The equivalent resistance is
(a) 20 W
(b) 4 W
(c) 5 W
(d) 10 W
Answer. A

Question. In the following circuit, find the equivalent resistance between A and B is (R = 2 W)

(a) 10 Ω
(b) 5 Ω
(c) 2 Ω
(d) 4 Ω
Answer. A

Question. In the given circuit, the current in each resistor is

(a) 3 A
(b) 6 A
(c) 9 A
(d) 18 A
Answer. A

CBSE Class 10 Physics Chapter 12 Electricity Assertion & Reasoning Based MCQs

For question numbers 46-55, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Both assertion and reason are true, and reason is correct explanation of the assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of the assertion.
(c) Assertion is true, but reason is false.
(d) Assertion is false, but reason is true.

Question. Assertion : The connecting wires are made of copper.
Reason : The electrical conductivity of copper is high.
Answer. A

Question. Assertion : A bird perches on a high power line and nothing happens to the bird.
Reason : The circuit is incomplete for the bird sitting on high power line.
Answer. A

Question. Assertion : The coil of a heater is cut into two equal halves and only one of them is used into heater. The heater will now require half the time to produce the same amount of heat.
Reason : The heat produced is directly proportional to square of current.
Answer. B

Question. Assertion : A current carrying wire should be charged.
Reason : The current in a wire is due to flow of free electrons in a definite direction.
Answer. D

Question. Assertion : Electrons always move from a region of lower potential to a region of higher potential.
Reason : Electron has a negative charge.
Answer. A