When electric current flows in a purely resistive circuit electri… - Vidyadip

Question

When electric current flows in a purely resistive circuit electrical energy gets fully converted into heat energy. The amount of heat produced (H) in the circuit is found to be directly proportional to (i) the square of current $\mathrm{I}^{2}$
(ii) the resistance $(R)$ of the conductor and (iii) the time $(t)$ for which current flows. In other words $H=I^{2} R t$.
Electrical devices such an electric fuse, electric heater, electric iron etc. are all based on this effect called heating effect of electric current.
a. List two properties of heating elements.
b. List two properties of electric fuse.
c. Name the principle on which an electric fuse works. Explain how a fuse wire is capable of saving electrical appliances from getting damaged due to accidently produced high currents.
OR
The power of an electric heater is 1100 W . If the potential difference between the two terminals of the heater is 220 V , find the current flowing in the circuit. What will happen to an electric fuse of rating 5 A connected in this circuit?

✓

Answer

a. Higher resistivity than pure metals
Do not oxidise (burn) at high temperature.
b. Higher resistivity than pure metals
Low melting point.
c. Heating effect of electric current
When high current flows in the circuit accidently, the fuse wire melts and breaks the circuit.
OR
$\mathrm{P}=1100 \mathrm{~W} ; \mathrm{V}=220 \mathrm{~V}, \mathrm{I}=$ ?
$\mathrm{P}=\mathrm{VI}$
$\mathrm{I}=\frac{P}{V}=\frac{1100 \mathrm{~W}}{220 \mathrm{~V}}=5 \mathrm{~A}$
No effect on the fuse of 5A rating.

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