The electric resistance of a particular wire of iron is R. If its length and radius are doubled, then:
1. | The resistance will be halved and the specific resistance will remain unchanged |
2. | The resistance will be halved and the specific resistance will be doubled |
3. | The resistance and the specific resistance, will both remain unchanged |
4. | The resistance will be doubled and the specific resistance will be halved |
Resistances n, each of r ohm, when connected in parallel give an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have resistance in ohms, equal to:
1.
2. R/n
3. nR
4. n2 R
When a wire of uniform cross-section a, length l, and resistance R is bent into a complete circle, the resistance between any two diametrically opposite points will be:
1. R/2
2. R/4
3. R/8
4. 4R