A current flow in wire of resistance 5 ohm having potential difference

1.	A current flow in wire of resistance 5 ohm having potential difference 7 volt in 20 minutes the heat produced is
Answer» Given : Resistance of wire =5 Ω Potential difference =7 V TIME ,t =20min=1200sec To Find : Heat produced in a wire Solution : We have to find heat produced in a wire . According to the JOULE's LAW of Heating The heat produced in a wire is directly proportional to: Square of current Resistance of wire time (t) , for which current is passed. $\sf\implies\:H=I^2RT$ We KNOW that,Ohm's law : $\tt\:I=\dfrac{V}{R}$ $\sf\implies\:H=(\dfrac{V}{R})^2\times\:RT$ $\sf\implies\:H=\dfrac{V^2}{R}\times\:T$ Now put the given values $\sf\implies\:H=\dfrac{7\times7}{5}\times\:1200$ $\sf\implies\:H=49\times240$ $\sf\implies\:H=11,760J$ We know that 1J = 0.239 Calorie ⇒11,760 JOULES = 2810.7 Calories( aprrox) Therefore, Heat produced in a wire is 2810 calories .