Some students carry out investigations with an electric motor - Edexcel - GCSE Physics - Question 1 - 2012 - Paper 1

To calculate the input power, we use the formula:

$P = V imes I$

where:

• $P$ is the power in watts (W)
• $V$ is the voltage in volts (V)
• $I$ is the current in amperes (A)

Substituting in the values: $P = 6 ext{ V} imes 0.5 ext{ A} = 3 ext{ W}$

Thus, the input power to the motor is 3 W.

To find the wasted energy, we subtract the energy transferred to the weight from the input energy:

$ext{Wasted energy} = ext{Input energy} - ext{Energy transferred}$ $= 200 ext{ J} - 50 ext{ J} = 150 ext{ J}$

Thus, 150 J of energy is wasted.

Efficiency can be calculated using the formula:

ext{Efficiency} = rac{ ext{Useful output energy}}{ ext{Input energy}} imes 100 ext{\%}

Substituting the values: = rac{50 ext{ J}}{200 ext{ J}} imes 100 ext{\%} = 25\%

Therefore, the efficiency of the motor is 25%.