You could use a higher or lower volt battery to control the brightness of a light bulb or the spin of a motor in a circuit. Volts are the measure of potential energy in a battery; the higher the volts, the more potential energy. Or you could add or remove resistors from the circuit, as resistors reduce the amount of electricity flowing through a circuit. Or you could add a potentiometer to the circuit and change the amount of electricity flowing by adjusting a knob or a slider. Students might even mention using a transistor in an integrated circuit to boost the electrical signal.