Class 8 (Science Assignment)

 

Electricity and Magnetism

Electricity and magnetism are closely related forms of energy. Electric current is the flow of electric charge through a conductor. Materials such as copper and aluminum are good conductors of electricity, while rubber, plastic, and dry wood are generally poor conductors.

A simple electric circuit consists of a source of electricity, such as a cell or battery, connecting wires, and a device such as a bulb. The bulb glows only when the circuit is closed, allowing current to flow through it. A switch is used to open or close an electric circuit.

Electric current can produce a magnetic effect. When electric current passes through a wire, a magnetic field is produced around the wire. A coil of insulated wire carrying current behaves like a magnet and is called an electromagnet. Electromagnets are useful because their magnetic effect can be switched on and off. They are used in electric bells, relays, cranes for lifting iron objects, and some electrical devices.

Magnets have two poles: north and south. Like poles repel each other, while unlike poles attract each other. A compass works because its magnetic needle aligns approximately along the north-south direction of Earth’s magnetic field. Thus, electricity and magnetism are important in many devices used in our daily lives.

A. Short-Answer Questions

1. What is electric current?
2. What is the function of a switch in an electric circuit?
3. What happens when electric current passes through a wire?
4. What is an electromagnet? Write one use of it.
5. What happens when two unlike magnetic poles are brought close together?

B. Multiple-Choice Questions

1. Which of the following is a good conductor of electricity?
A. Rubber
B. Plastic
C. Copper
D. Dry wood

2. An electric bulb glows when the circuit is:
A. open
B. closed
C. broken
D. disconnected

3. The passage of electric current through a wire produces:
A. only heat
B. a magnetic effect
C. only light
D. sound only

4. Which device uses an electromagnet?
A. Electric bell
B. Glass
C. Wooden ruler
D. Thermometer

5. What happens when unlike poles of two magnets are brought together?
A. They repel
B. They attract
C. They disappear.
D. They lose their magnetism