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CBSE Worksheet-45

Class VII Science (Electric Current and its Effects)

1. Electric current is the flow of

a. Proton

b. Electron

c. Neutron

d. Positron

2. Which of the following materials is a conductor?

a. Silver

b. Plastic

c. Cloth

d. Rubber

3. A device which prevents or allow the current to flow through it

a. Motor

b. Conductor

c. Switch

d. Terminal

4. When two or more cells are joined together it forms a

a. Dynamo

b. Transistor

c. Battery

d. Insulator

5. Match the following:

Column A Column B

a. Switch i. Heating effect

b. Electric cell ii. Insulator

c. Rubber iii. Produce electricity

d. Copper iv. Close and open the circuit.

e. Electric heater v. Conductor

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6. Fill in the blanks.

a. A group of two or more cell is called a ---------------------.

b. A device that breaks the circuit is called a----------------.

c. In electric circuit the electrons flow from ------------ terminal to the -----------

terminal.

d. Metals are --------------- conductor.

e. A device which converts electric energy into light energy is -------------.

7. Why do we use nichrome in an electric heater?

8. What is a fuse? Write its function?

9. Write difference between a cell and a battery?

10. Give one word for the following:

a. Path of electric circuit

b. A device that create potential difference.

c. Coming together of live and neutral wire in a circuit.

d. A safety device that protects appliances from overloading and short circuit.

e. Magnet produced by electricity.

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Answer key

1. b

2. a

3. c

4. c

5. (a) (iv), (b) (iii), (c) (ii), (d) (v), (e) (i).

6. (a) Battery (b) switch (c) negative, positive (d) good (e) bulb.

7. Nichrome is an alloy having high resistivity. The melting point of nichrome is also very

high. So, nichrome is used as coil in electric heater.

8. Fuse is a safety device made up of alloy having low melting point. It is connected in

series in the circuit. It protects the circuit and electrical appliances in case of excess of

current in the circuit.

9. A cell is a device that creates potential difference in the circuit to flow the current in

the circuit. Combination of two or more cell in series is called a battery.

10. (a) Electric circuit

(b) Battery or cell

(c) Short circuit

(d) Fuse

(e) Electromagnet.