Q: A 5 amp fuse wire can withstand a maximum power of 1 W in circuit. The resistance of the fuse wire is

Given: Power \$(P) = 1 \space W\$Current \$(I) = 5 \space A\$Resistance \$(R) = ?\$The power of a resistor is the rate of flow of energy through it. Maximum power is the limiting energy flow after which the resistor (or wire here) would fuse. We know that, \$P=I^2R\$\$\Rightarrow R=\dfrac{P}{I^2}=\dfrac{1W}{25A^2}=0.04\Omega\$

Question 1

Why are alloys commonly used in electrical heating devices? Give reason.

Accepted Answer

Alloys generally have high melting point as compared to the individual elements. The electrical heating devices must have high melting point so that they do not melt even at high temperature when an electrical current passes through the device. Thus alloys are used in electrical heating device.

Question 2

Mark the correct reason/s why nichrome is used for making heating element of electrical appliances.

Accepted Answer

Nichrome is used for making heating element of electrical appliances. Because nichrome does not oxidize and burn easily at high temperature i.e.it has higher melting and boiling point than metals. Thus it does not melt even when a large amount of heat is produced due to passage of current. Moreover, It has higher resisistivity and consequently a higher resistance.Therefore, it will resist the flow of charges more, and lead to development of heat faster.

Question 3

Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse. Why is it that a burnt out fuse should be replaced by another fuse of identical rating?

Accepted Answer

A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. Otherwise, the appliances or the circuit may be damaged. When current in the circuit exceeds the value of fuse rating, the fuse wire burns due to overloading. This causes a gap in the circuit and the current stops flowing in the circuit. This is done due to the reason so that the circuit or the appliances to be connected in the circuit continue functioning without any damage in future.

Question 4

Fuse wire must have high resistance and low melting point.

Accepted Answer

Fuse is used for small current flow only.

Question 5

What are the characteristics of heating element used in electric heating device?

Accepted Answer

Characteristics of heating element used in electric heating device are :(1) : It must have high resistivity so that it produces more heat even if low current is flowing through it.(2) : It must have high melting point so that it does not melt even at high temperatures.(3) : It must have low temperature coefficient of resistance.That's why Nichrome, an alloy of chromium and nickel, is used as heating element in electric heating device as nichrome has all the above characteristics.

Question 6

State difference between the wire used in the element of an electric heater and in a fuse wire.

Accepted Answer

The wire used in the element of electric heater has a high resistivity and have a high melting point, i.e. even at a high temperature element do not burn while fuse wire have a low melting point and high resistivity.

Question 7

Write three safety measures in using electricity.

Accepted Answer

1) Never touch electrical equipment with wet hands.When working with electricity do not stand on metal, wet concrete or wet ground.2)Always wear rubber glows and slippers while working with electricity board.3)Disconnect electrical gadgets when not in use and at the time of lightning and thundering.4) Repair and maintenance of electrical fuses and gadgets should be done time to time.5) Faulty electrical wires and cords should never be used.

Question 8

A 5 amp fuse wire can withstand a maximum power of 1 W in circuit. The resistance of the fuse wire is

Accepted Answer

Given: Power $(P) = 1 \space W$Current $(I) = 5 \space A$Resistance $(R) = ?$The power of a resistor is the rate of flow of energy through it. Maximum power is the limiting energy flow after which the resistor (or wire here) would fuse. We know that, $P=I^2R$$\Rightarrow R=\dfrac{P}{I^2}=\dfrac{1W}{25A^2}=0.04\Omega$

Question 9

Choose the statement which is not correct in the case of an electric fuse.

Accepted Answer

In case of electric fuse, there is only a maximum limit on the current which can safely flow in the electric circuits. There is a minimum limit on the current which can safely flow in the electric circuits.

Question 10

Which of the following are the properties of fuse wire?

Accepted Answer

All the given options hold true for fuse wire. A fuse wire should have these characteristics:low melting point, high conductivity and least deterioration due to oxidationIt is connected in series with main supply.

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Applications of Heating Effect of Electric Current

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Application of Heating Effect of Electrical Current

Why are alloys commonly used in electrical heating devices? Give reason.

Mark the correct reason/s why nichrome is used for making heating element of electrical appliances.

Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse. Why is it that a burnt out fuse should be replaced by another fuse of identical rating?

Fuse wire must have high resistance and low melting point.

Fuse is used for small current flow only.

Fuse wire must have high resistance and low melting point.

What are the characteristics of heating element used in electric heating device?

State difference between the wire used in the element of an electric heater and in a fuse wire.

Write three safety measures in using electricity.

A 5 amp fuse wire can withstand a maximum power of 1 W in circuit. The resistance of the fuse wire is

Choose the statement which is not correct in the case of an electric fuse.

Which of the following are the properties of fuse wire?