CBSE Class 10 Answered
A copper wire ha a diameter of 0.5mm and a resistivity of
ohm cm. How much of this wire will be necessary to make a 10 ohm coil? How much does the resistance change if the diameter is doubled?
Asked by adalroshan2464 | 28 Mar, 2019, 14:54: PM
a). As we know resistance of a resistor is define as R = (ρ×l)/A where ρ is resistivity of the material, l is the length of the conductor and A is the cross section area
For given setup
A = π × r^2= 3.14× 0.25×0.25×10^-6 = 1.96 × 10^-7
So putiing all the values we get
10 = (1.6× 10^-8 × l)/1.96 × 10^-7
We get the value of l = 125 m
b). As from the earlier statement we can see that resistance of the wire is inversely proportional to the area of the cross section. So if we increase the radius the resistance will decrease and vice versa
So if the radius is doubled the area becomes 4 times as of its initial value , so the resistance of wire become = 10/4 = 2.5 Ω
Answered by Ankit K | 28 Mar, 2019, 22:19: PM
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