A motor is connected to a power supply which supplies 6 amperes of current with a 20-volt potential difference. The motor is used to lift a mass which is 40 kg. The motor has a 10% efficiency rating.
The power provided by a power supply is given by
P = IΔV
where P is power in Watts, I is current in amperes, and ΔV is the potential difference in volts. (Use g = 10 m/s2.)
How long would it take to bring the mass to the same height if the current and the potential difference were both doubled? (Assume constant efficiency.)