Question

on passing a current of 3 ampere in an electric heater for 4 minut 540 kilo joule heat is produced calculate the resistance of heaters wire
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Answer 1

Answer:

Current i=4 A

Resistance R=40 Ω

time t=8×60 second

Heat generated H=i2Rt

=16×40×8×60 J

16×40×8×60/1000kJ

= 307.2 kJ

Answer 2

The resistance of the wire of the electric heater is 250 ohms.

Given,

Current passing through the electric heater=3 ampere

Time for which the current passes through the electric heater= 4 minutes.

Heat produced by the electric heater= 540 kilo Joules.

To find,

the resistance of the wire of the electric heater.

Solution:

• According to the Joule's law of heating, the heat produced in a resistor is given as:
• H=I^2Rt.
• where, H-heat produced, I-current that passes through the resistor, R-resistance and t-time for which the current passes.
• 1 kilo Joules=1000 Joules.

First, 4 minutes need to be converted into seconds,

=4 x 60 seconds

=240 seconds.

The resistance of the wire will be:

H=I^2Rt

540 x 1000=3 x 3 x R x 240

540000=2160R

R=540000/2160

R=250 ohms.

Hence, the resistance is 250 ohms.

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