Class 7 Science Chapter 10 MCQ

Here are all the statements are correct. Hence your answer will be option [D].

The electric bulb has very thin filament of tungsten metal. The filament of an electric bulb has a high resistance. When electric current passes through the very thin, high resistance filament of an electric bulb, heat is produced in it. Due to this the filament of electric bulb gets heated to a very high temperature and starts glowing.

Here are all the statements are correct. Hence your answer will be option [D].

Portable generators as well as inverters has very high voltage of 220 volts.

The electric bulb or electric lamp which we use for producing light works on the heating effect of electric current. An electric bulb is basically used for producing light but it also gives out heat. In fact, a major part of the electricity consumed by the filament of an electric bulb is converted into heat (due to which the bulb becomes hot), only a small part of electricity is converted into light.

A fuse is a safety device which prevents electric fires and damage to electrical appliances due to excessive flow of current. A fuse works on the heating effect of current. A fuse consists a short length of a thin, tin-plated copper wire having low melting point. If due to some reason the current in household wiring suddenly becomes too large or exceeds the safe limit, then the fuse will blow off or cut or melt (its wire will be we get heated to much, melt and break the circuit). When the fuse wire breaks, electricity supply in the household wiring is automatically cut off before any damage can be done to the rest of wiring or to the electrical appliances being used.

The magnet made by using electric current is called an electromagnet. Remember, only iron is used for making electromagnets because when current is switched off in the coil of an “electromagnet made of iron pieces” then the iron piece loses all its magnetism. Steel is not used for making electromagnets because when current is switched off from the coil of an electromagnet made of a steel pieces, it does not lose all its magnetic. The still remains the magnetism and becomes a permanent magnet.

The symbol for representing a battery for three cells will have three pairs of long and short parallel lines connected to one another.

MCB stand for miniature circuit breaker. These days MCBs or miniature circuit breakers are being used increasingly in household electric wiring, in place of traditional fuses. MCB does not work on the heating effect of current. MCB works on the magnetic effect of current.

The heating elements of most of the electric heating appliances such as, electric iron, electric kettle, electric geyser, electric oven, hot plates and hair dryer etc., cannot be seen by us because they are concealed inside the body of these appliances.

The electric bulb or electric lamp which we use for producing light works on the heating effect of electric current. An electric bulb is basically used for producing light but it also gives out heat. In fact, a major part of the electricity consumed by the filament of an electric bulb is converted into heat (due to which the bulb becomes hot), only a small part of electricity is converted into light. The production of heat by an electric bulb is not desirable because it leads to the wastage of electricity.

Here all the statements are correct. Hence your answer will be option [D].

We use a thin wire in a fuse because it has a much greater resistance than the rest of connecting wires. When a fuse gets blown or breaks a new fuse has to be fitted in its place to restore the electricity supply in the household circuit. We should not use a thick wire as a fuse wire because it will have a low resistance and then it will not get heated to its melting point easily.

MCB stand for miniature circuit breaker. These days MCBs or miniature circuit breakers are being used increasingly in household electric wiring, in place of traditional fuses. MCB does not work on the heating effect of current. MCB works on the magnetic effect of current.

The fluorescent tube lights and compact fluorescent lamps do not have filaments. Fluorescent tube lights and compact fluorescent lamps do not work on the heating effect of current. The fluorescent tube light on lamp contains mercury vapor, which is a kind of gas.

Here all the statements are correct. Hence your answer will be option [D].

The electric bulb has very thin filament of tungsten metal. The filament of an electric bulb has a “high resistance”. When electric current passes through the very thin, high resistance filament of an electric bulb, heat is produced in it. Due to this the filament of electric bulb gets heated to a very high temperature and starts glowing.

Here all the statements are correct. Hence your answer will be option [D].

When the switch is in off position, circuit is incomplete. It is said to be open and therefore, no current flows through it.

Here all the statements are correct. Hence your answer will be option [D].

Here all the statements are correct. Hence your answer will be option [D].

Here all the statements are correct. Hence your answer will be option [D].

The electric bell works on the magnetic effect of current, not the heating effect of current.

Here all the statements are correct. Hence your answer will be option [D].

For using electric gadgets or appliances or circuit, we have to turn the switch in ON position. Therefore, precautions given in option [D], need not to be considered.