Question

5. State Joule's law of heating. How much heat energy is dissipated if 200mA current is passed
through a 10 ohm resistor in a minute?

Answer 1

Explanation:

Joule's law of heating states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the electric current passing through the conductor.

The power input is (P)=VI

Thus, the current, I=

V

P

When heat is at the maximum rate, I=

220

840

=3.82A

The resistance of the electric iron, R=

I

V

==

3.82

220

=57.59Ω

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Answer 2

$\sf\huge\underline{Answer :-}$

State Joule's law of heating.

Joule's law of heating effect of current are :-

• If the resistance of the conductor and time of flow of the current remain constant then the heat produced in the conductor will be directly proportional to the square of the the current strength. i.e, H ∝ I²

• If the currents friend and time of flow of current remain constant then the heat produced in the conductor is directly proportional to resistance of the conductor. i.e, H ∝ R

• If the resistance of the conductor and strength of current remain constant then the heat produced in the conductor will be directly proportional to the time of flow of the current. H ∝ t

From the above three laws, by the rule of joint variation :-

=> H ∝ I²Rt

=> H = I²Rt/J [where J is the mechanical equivalent of heat and it's value is 4.2 J/cal]

If all the given values are in SI system, then value of J will be 1. Therefore, H = I²Rt

____________________________________

How much heat energy is dissipated if 200mA current is passed through a 10 ohm resistor in a minute?

= Given,

• I = 200 ma = 0.2 A
• R = 10 ohm
• t = 1 minute = 60 seconds

We know that,

=> H = I²Rt

= (0.2)² × 10 × 60

= 24 Joules.

Hence, the heat energy dissipated will be 24 Joules.