NCERT Class 7 Science Chapter 14 Electric Current And Its Effects | Important Questions
Here are important questions from NCERT class 7 Science Chapter 14 Electric Current and Its Effects.
1. An electric cell has a …………………… and a ……………………….. terminal.
Positive and negative
2. In the symbol of an electric cell, the longer line represents the ……………………… terminal and the thicker, shorter line represents the ……………………….. terminal.
Positive and negative
3. Wires used to connect the various components in a circuit are represented by …………………………….
Lines
4. What is a battery?
A battery is a combination of two or more cells. In a battery, the positive terminal of one cell is connected to the negative terminal of the next cell.
5. What is the heating effect of the electric current?
When electric current passes through a wire, it gets hot. This is called the heating effect of the electric current.
6. Name some appliances that make use of the heating effect of the electric current.
Electric room heater and electric heater used for cooking.
7. What is an element?
All appliances that make use of the heating effect of the electric current contain a coil of wire. This coil of wire is called an element.
8. Why are wires of different material and different length or thickness used for different purposes?
The amount of heat produced by a wire depends on its material, length and thickness. Hence, wires of different material and different length or thickness are used for different purposes.
9. Incandescent electric bulbs are not energy efficient. Why?
Incandescent electric bulbs do produce light but they also give a lot of heat. That means these bulbs use a part of the electricity for producing heat. This results in the wastage of electricity because a light bulb is not required to give heat. Hence, these bulbs are not energy efficient.
10. What is the full form of LED?
Light Emitting Diode
11. What are CFLs?
These are Compact Fluorescent Lamps.
12. Which of the following is the most energy efficient?
a) LEDs, b) incandescent bulbs, c) CFLs, d) Fluorescent tube lights
LEDs
13. What is an electric fuse?
A fuse is a device inserted in all electrical circuits to ensure that the current passing through the circuit does not exceed the safe limit. When current exceeds this limit, the fuse will blow off and break the circuit.
14. What causes excessive current in a circuit?
One of the causes of excessive current in a circuit is the direct touching of wires. This may happen if the insulation on the wire comes off. This may cause a short circuit. If several devices are connected to a single socket, it can also cause excessive current in the circuit.
15. What are MCBs?
MCB is the short form of Miniature Circuit Breaker. These are switches which automatically turn off when current in a circuit exceeds the safe limit. When you turn them on, the circuit is complete once again. MCBs are now increasingly being used instead of electric fuses.
16. Who was the first person to notice that a compact needle deflects when current passes through it?
Hans Christian Oersted
17. What is the magnetic effect of the electric current?
When electric current passes through a wire, it behaves like a magnet. This is the magnetic effect of electric current.
18. What are electromagnets?
When electric current passes through a coil, it behaves like a magnet. When current is switched off, the coil will lose its magnetism. Such coils are called electromagnets.
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