CBSE Class 7 Science Electric Current and its effects Assignment

Question. A small pocket radio can be operated either using 4 small cells (batteries) or using mains electric power.
How is this possible?
(a) The voltage from both sources is the same.
(b) The radio works within a large range of voltages.
(c) The electric power charges the cells that operate the radio.
(d) The mains electric power voltage is reduced to operate the radio.

Answer : D

Question. Will a battery that is used in a torch light up a regular 60W bulb used in homes
(a) Yes, it will and the bulb will glow quite brightly.
(b) Yes, it will but the bulb will glow dimly.
(c) No, it will not because a battery does not produce electricity.
(d) No, it will not because the current will not be sufficient.

Answer : D

Question. The setup shown here is to be used by group of students to classify materials as conducting and non-conducting. The materials they want to classify are.  What is the very FIRST thing that they should do before starting to test any materials?

(a) Place the items one by one between the open leads given and if the bulb glows then list them as conductors.
(b) Check with a person working in the laboratory whether the given materials are conductors.
(c) Place a known insulator between the leads given and check if the bulb glows.
(d) Without placing anything between the open leads, connect the circuit and check if the bulb lights up.

Answer : D

Question. An open box has two mirrors arranged as shown, with a ray of light incident on one of the mirrors. How many times will the ray reflect before it leaves the box?

(a) 2
(b) 3
(c) 5
(d) The ray will never leave the box

Answer : D

Question. Which phenomenon of light is illustrated by the pair of boards shown here?

(a) Refraction
(b) Lateral displacement
(c) Dispersion
(d) Lateral inversion

Answer : D

Question. Which of the following will be the shadows that Trupti will see on the translucent screen, if a sphere is held between two-point sources of light and the screen?

Answer : D

Question. Neha focused a magnifying glass on to a tissue paper and held it. After a while, the tissue paper caught fire. Identify the statement that provides the correct explanation for this observation.
(a) Neha lit the tissue paper.
(b) The magnifying glass focuses the heat from the Sun's radiation.
(c) The magnifying glass is a good conductor of heat and transmits the heat to the paper.
(d) Air is a good conductor of heat and transmits the heat to the paper.

Answer : B

Question. Here is a scale drawing of an arrangement of a LIGHT SOURCE, BOOK and SCREEN in a darkened room. Which of the options below shows the correct situation at points P, Q, R and S on the screen?

(a) A
(b) B
(c) C
(d) D

Answer : B

Question. Which one of the diagrams below correctly shows the path of the reflected ray?

Answer : C

Question. Veena observes the time in the clock shown in picture, through a MIRROR and thinks it is 9:40. What would be the actual time? 

(a) 3:20:00 AM
(b) 9:40:00AM 
(c) 3:40:00 AM
(d) 2:20:00 AM

Answer : D

Question. Shown in picture is the flag of a country. Blue, Green and Red are primary colours and Yellow = Red + Green. If the above flag is seen through a red filter, it will look like

Answer : D

Question. Which of these rays shown here will strike each mirror either directly or after reflection? 

(a) A
(b) B
(c) C
(d) D

Answer : A

Question. If our eyes did not have tear glands, what would happen?
(a) Nothing. These glands are not really necessary. 
(b) The only effect would be that we would not be able to cry. 
(c) We would become blind immediately since tears are needed to see. 
(d) Our eyes would get damaged since the tears provide lubrication. 

Answer : D

Question. A crowd is watching a firework display. They see the firework explode and then hear the noise of the explosion a little later. Why does this happen?
(a) Light travels faster than sound. 
(b) Sound travels upwards and then moves towards the crowds.
(c) The sound is produced after the light.
(d) Sound is blocked by the layers of air it passes through.

Answer : A

Question. George is running towards the finish line in a race. The sun is casting his shadow as shown. In which direction is George running? 

(a) definitely north-west
(b) either north-east or south-west
(c) definitely south-west
(d) it is not possible to tell from the given information

Answer : B
 

Q.1 Fill in the blanks :

a) The combination of two or more cells is called a ________________.

b) The coil of wire used in electric heaters is called an _______________.

c) A current carrying coil of an insulated wire wrapped around a piece of iron is called an _____________.

d) Magnetic effect of Electric current was discovered by a scientist named._______

e) When electric current flows through a wire, it gets heated which is termed as the ______________ effect of electric current.

Q.2 Match the following :

Column I                    Column II

1. MCB                  a. Nichrome

2. ISI mark            b. Miniature Circuit Breaker

3. CFL                   c. Tungsten

4. Element            d. Compact Fluorescent Lamps

5. Filament           e. Bureau of Indian Standards

Answers : 1. 2. 3. 4. 5.

Q.3 Write the symbol for the following Electric components :

1. Electric Cell ...............................

2. Electric Bulb ...............................

3. Switch ‘ON’ ...............................

4. Switch ‘Off’ ...............................

5. Battery ...............................

6. Wire ...............................

Q.4. Observe and write whether Open Circuit of Closed Circuit :

1.
Answer :____________________

2.
Answer :____________________

3.
Answer :____________________