Question

An energy source forces a constant current of 2 A for 10 s to flow through a lightbulb. If 2.3 kJ is given off in the form of light and heat energy, calculate the voltage drop across the bulb.

Answer 1

The energy can be expressed in terms of power and time in the following form:

$$E=Pt.$$

The power can be expressed in terms of voltage and current:

$$P=VI,\\ E=VIt,,\\\space\\ V=\frac{E}{It}=\frac{2300}{2·10}=115\text{ V}.$$