Question

A hand crank generator is used to power a light bulb. The person turning the crank uses 22 Newtons of input force to turn the crank 8 revolutions in 3 seconds. Each revolution of the crank equals 0.3 meters of distance that his hand moves. A multimeter connected to the light bulb records 0.08 amps of current and 9.04 volts.

1. Calculate the input power of the hand crank generator in Watts.

2. Calculate the output power of the hand crank generator in Watts.

3. Calculate the efficiency of the hand crank generator.

Answer 1

1. The input power is 17.6 Watts

2. The output power is 0.7232 Watts

3.The efficiency of the hand crank generator is approximately 4.109%

Step-by-step explanation:

The given parameters are;

The force with which the crank generator is turned = 22 Newtons

The rate at which the crank is turned = 8 revolutions per 3 seconds

The distance the hand moves during each revolution = 0.3 meters

The current recorded by the multimeter = 0.08 amps

The voltage recorded by the multimeter = 9.04 volts

1. Power = The rate of doing work = Work done/(Time taken to do the work) = Force × Distance/Time

∴ The power input of the hand crank generator = 22 × 0.3 × 8/3 = 17.6 Watts

2. The power output to the bulb, P, is given by the formula for electrical power as follows;

Power = Current, I × Voltage V

∴ P = 0.08 × 9.04 = 0.7232 Watts

3. Efficiency in percentage = Output/Input × 100

Therefore, the efficiency of the hand crank generator = )Output power/(Input power)) × 100 = (0.7232/17.6) × 100 ≈ 4.109%