Q1.
Put the cells back in a different order. Also, try reversing the direction of one cell. Then, slide the switch and check whether the lamp glows in each case.
Answer
The lamp glows in only one of the arrangements — the one in which the + terminal of one cell touches the – terminal of the other.
| How the two cells are placed | Do the cells help or oppose? | Lamp |
|---|---|---|
| – + – + | + of first meets – of second — they help each other | Glows |
| – + + – | + meets + — they oppose each other | Does not glow |
| + – – + | – meets – — they oppose each other | Does not glow |
| + – + – | – of first meets + of second — they help each other | Glows |
Why it happens: Two cells joined + to – add their pushes, so the current through the filament is strong enough to make it glow. Two cells joined + to + (or – to –) push in opposite directions; their effects cancel and almost no current flows.