Science
(i) State Joule's law of heating. Express it mathematically when an appliance of resistance R is connected to a source of voltage V and the current I flows through the appliance for a time t.
(ii) A 5 Ω resistor is connected across a battery of 6 volts. Calculate the energy that dissipates as heat in 10 s.
Current Electricity
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Answer
(i) Joules law of heating states that the heat dissipated across a resistor is directly proportional to
- the square of the current flowing through it
- resistance of the conductor
- duration of flow of current
i.e., H = I2Rt
(ii) Given,
Resistance (R) = 5 Ω
Voltage (V) = 6 V
Time (t) = 10 s
From ohm's law :
V = IR
6 = I x 5
I = = 1.2 A
Energy dissipated (H) = I2Rt
Substituting we get,
H = 1.2 x 1.2 x 5 x 10 = 72 J
Hence, energy dissipated = 72 J.
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