An electric pottery wheel receives 600 J from the mains supply in each second of operation. Its operating record gives running values for the energy dissipated into the thermal energy stores of the wheel and its surroundings.
| Elapsed operating time in s | Energy dissipated so far in J |
|---|---|
| 3 | 720 |
| 9 | 1980 |
What is the efficiency of the wheel during the final 6 s shown?
0.650.650.65
0.350.350.35
0.600.600.60
0.630.630.63