Question

When the current is doubled in a heating device and time is halved, the
heat energy produced is??
(a) 4 times
(b) 2 times
(c) ½ times
(d) ¼ times

Answer 1

Answer:

4 times

Explanation:

Energy(Power*Time)is measured in joules and by including time in the power the energy dissipated by a component or circuit can be calculated.

Answer 2

When the current is doubled in a heating device and time is halved, the heat energy produced is (b) 2 times.

• When current is passed through a heating device with resistance R, heat energy is dissipated. This is called the heating effect of electric current.
• If the current i flows through the device for a time t, then the heat energy produced = i²Rt.
• Since the current is doubled (2i) and time is halved (t/2),

     ⇒ The new heat energy produced = (2i)²R(t/2)

       = 4i²Rt/2

      = 2i²Rt

    Hence the current increases from i²Rt to 2i²Rt.