A filament lamp is tested before and after a modification. The lamp is intended to produce visible light. Its only energy outputs are visible light, infrared radiation and heating of the surroundings.
| Test | Total electrical energy supplied | Efficiency | Energy transferred by infrared radiation |
|---|---|---|---|
| Before modification | 2.50 kJ | 12% | 1.85 kJ |
| After modification | 2.50 kJ | not given | 1.70 kJ |
The energy transferred by heating the surroundings is the same in both tests.
Calculate the energy transferred by heating the surroundings before the modification.
Calculate the efficiency of the lamp after the modification.