Advertisements
Advertisements
Question
A metal wire of resistance 6 Ω is stretched so that its length is increased to twice its original length. Calculate its new resistance.
Advertisements
Solution
R1 = 6Ω, R2 = ?
l1 = l, l2 = 2l
a1 = a, a2 = `a/2`
p1 = p2
`(R_1a_1)/(l_1) = (R_2a_2)/(l_2)`
`6xxa/l = (R_2xxa/2)/(2l)`
`6 = (R_2xx1/2)/2`
`6 = R_2 xx1/2xx1/2`
6 × 2 × 2 = R2
R2 = 24Ω
RELATED QUESTIONS
If the equivalent resistance is to be increased, then the number of resistances should be connected in
- Series
- Parallel
- Mixed arrangement
- None of the above
An electrical appliance has a resistance of 25 Ω. When this electrical appliance is connected to a 230 V supply line, the current passing through it will be:
(a) 0.92 A
(b) 2.9 A
(c) 9.2 A
(d) 92 A
When a 4 Ω resistor is connected across the terminals of a 12 V battery, the number of coulombs passing through the resistor per second is:
(a) 0.3
(b) 3
(c) 4
(d) 12
How does the presence of impurities in a metal affect its resistance?
Write down an expression for the resistance of a metallic wire in terms of the resistivity.
Calculate the combined resistance in each case:
Name the following substances:
(i) Showing low resistivity,
(ii) Showing very high resistivity,
(iii) Showing moderate resistivity.
State the effect of rise in temperature on the resistance of semi-conductors.
Calculate the equivalent resistance between P and Q from the following diagram:
Calculate the quantity of heat that will be produced in a coil of resistance 75 Ω if a current of 2A is passed through it for 2 minutes.
