Q. No.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 \(r~\text{ohm},\) when connected in parallel give an equivalent resistance of \(R~\text{ohm}.\) If these resistances were connected in series, the combination would have resistance in \(\text{ohms}\) equal to:
1. \(\dfrac{R}{n^2}\)
2. \(\dfrac{R}{n}\)
3. \(nR\)
4. \(n^2R\)
The current in \(8~\Omega\) resistance is (in the figure below):
1. \(0.69\) A
2. \(0.92\) A
3. \(1.30\) A
4. \(1.6\) A
If the power dissipated in \(5~\Omega\) is \(20~\text{W}\) then the power dissipated in \(4~\Omega\) is:
1. \(4~\text{W}\)
2. \(6~\text{W}\)
3. \(10~\text{W}\)
4. \(20~\text{W}\)
1. \(3~\Omega\)
2. \(6~\Omega\)
3. \(12~\Omega\)
4. \(9~\Omega\)
The terminal potential difference of a cell is greater than its emf when:
| 1. | A battery of less emf is connected in its series. |
| 2. | A battery of higher emf is connected in its series. |
| 3. | A battery of higher emf is connected in its parallel. |
| 4. | A battery of less emf is connected in its parallel. |
In India, electricity is supplied for domestic use at \(220~\text{V}.\) It is supplied at \(110~\text{V}\) in the USA. If the resistance of a \(60~\text{W}\) bulb for use in India is \(R\), the resistance of a \(60~\text{W}\) bulb for use in the USA will be:
| 1. | \(2R\) | 2. | \(\dfrac{R}{4}\) |
| 3. | \(\dfrac{R}{2}\) | 4. | \(R\) |
A battery is charged at a potential of \(15\) V for \(8\) hours when the current flowing is \(10\) A. The battery on discharge supplies a current of \(5\) A for \(15\) hours. The mean terminal voltage during discharges is \(14\) V. The "Watt hour" efficiency of the battery is:
1. \(80\%\)
2. \(90\%\)
3. \(87.5\%\)
4. \(82.5\%\)
Five equal resistances each of resistance \(R\) are connected as shown in the figure below. A battery of \(V\) volts is connected between \(A\) and \(B\). The current flowing in \(AFCEB\) will be:
1. \(\frac{V}{R}\)
2. \(\frac{V}{2R}\)
3. \(\frac{2V}{R}\)
4. \(\frac{3V}{R}\)
A \(6\)-volt battery is connected to the terminals of a three-metre-long wire of uniform thickness and resistance of \(100\) ohms. The difference of potential between two points on the wire separated by a distance of \(50\) cm will be:
1. \(3\) V
2. \(1\) V
3. \(1.5\) V
4. \(2\) V
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