Question

For a given line voltage, four heating coils will produce maximum heat when connected
1. all in parallel
2. all in series
3. two parallel pairs in series
4. one pair in parallel with the two in series

Answer 1

Correct Answer - Option 1 : all in parallel

Suppose line voltage is V and resistance of each coil is R. Then if all connected in parallel, then the power will be 4V²/R as equivalent resistance is R/4. For all in series, equivalent resistance is 4R and power is V²/4R. For third case, equivalent resistance is R and power is V²/R. For last case, equivalent resistance is 5R/2 and power is 2V²/5R. Thus maximum heat is produced when all are connected in parallel.