1. The heating element of an electric iron is made up of ?

iron

aluminium

copper

nichrome

Answer: nichrome

Explanation:


2. A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of ?

less length

more radius

less radius

more length

Answer: more radius

Explanation:

In order to get the working of heater properly, fused wire of higher rating must be used.


3. If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then ?

R1 ? R2

R1 = R2

R2 < R1

R1 < R2

Answer: R2 < R1

Explanation:

More the power, lesser the resistance. Accordingly, R2 < R1


4. choose the statement which is/ are incorrect ?

In the series connection of electrical appliances, the overall resistance of the circuit increases too much due to which the current from the power supply is low.

In series circuit, if one electrical appliance stops working due to some defect, then all other appliances also stop working.

In series circuit, the appliances get the same voltage as that of the power supply line.

In series circuit, all the electrical appliances have only one switch due to which they cannot be turned on or off separately.

Answer: In series circuit, the appliances get the same voltage as that of the power supply line.

Explanation:

In series circuit, the appliances do not get the same voltage as that of the power supply line because the voltage is shared by all the appliances. The appliances get less voltage and hence do not work properly. For example, all the bulbs connected in series do not get the same voltage of 220 volts of the power supply line. They get less voltage and hence glow less brightly.


5. whether the statements are correct or not ?

When the potential difference is halved the current gets doubled.

When the length of a wire is halved, then its resistance also gets halved.

A long wire or long conductor has more resistance.

When the area of cross section of a wire is doubled its resistance gets halved.

Answer: When the potential difference is halved the current gets doubled.

Explanation:

The current is directly proportional to the potential difference applied across the ends of a conductor it means that if the potential difference across the ends of a conductor is doubled, the current flowing through it also gets doubled, and if the potential difference is halved the current also gets halved.


6. The electrical resistance of insulators is ?

zero

infinitely high

low

high

Answer: infinitely high

Explanation:


7. A cooler of 1500 W, 200 volt and a fan of 500 W, 200 volt are to be used from a household supply. The rating of fuse to be used is ?

7.5 A

10 A

5.0 A

2.5 A

Answer: 10 A

Explanation:

Total power used, P = P1 + P1 = 1500 + 500 = 2000 W. Current drawn from the supply,


8. The least resistance obtained by using 2 ohm, 4 ohm, 1 ohm and 100 ohm is ?

< 1 ohm

> 2 ohm

< 4 ohm

< 100 ohm

Answer: < 1 ohm

Explanation:

In parallel combination, the equivalent resistance is smaller than the least resistance used in the circuit.


9. The values of mA and microA are ?

10^–6 and 10^–3 A respectively

10^–3 and 10^–9 A respectively

10^–6 and 10^–9 A respectively

10^–3 and 10^–6 A respectively

Answer: 10^–3 and 10^–6 A respectively

Explanation:


10. The resistance of a resistor is reduced to half of its initial value. In doing so, if other parameters of the circuit remain unchanged, the heating effects in the resistor will become ?

four times

one-fourth

half

two times

Answer: two times

Explanation: