At a venue, an electric call bell is used to alert staff by sound. In a test, 1470 J of the energy supplied to the bell is transferred to thermal stores and the rest is transferred by sound.
An electric scooter accelerates from rest. In its test, 190 J is transferred to thermal stores and 10 J is transferred by sound. The rest is transferred to the kinetic energy store of the scooter and its rider.
| Device | Total energy supplied |
|---|---|
| call bell | 1.5 kJ |
| electric scooter | 1.0 kJ |
Calculate the efficiency of each device.