# At a voltage of 12 V, an amount of heat equal to 72 kJ is released on the heating coil for 10 minutes

September 30, 2021 | education

| **At a voltage of 12 V, an amount of heat equal to 72 kJ is released on the heating coil for 10 minutes. What is the electrical resistance of the coil?**

U = 12V.

t = 10 min = 600 s.

Q = 72 kJ = 72000 J.

R -?

The amount of heat Q that is released in a conductor with a current is determined by the Joule-Lenz law: Q = I * U * t, where I is the current strength, U is the current voltage, t is the time of its passage.

We express the current strength I according to Ohm’s law for a section of the circuit: I = U / R, where R is the resistance of the conductor.

The formula for the Joule-Lenz law will take the form: Q = U ^ 2 * t / R.

R = U ^ 2 * t / Q.

R = (12V) ^ 2 * 600s / 72000 J = 1.2 ohms.

Answer: the electrical resistance of the coil is R = 1.2 ohms.

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