Three resistances 2 Ω, 3 Ω and 4 Ω are connected in parallel. The ratio of currents passing through them when a potential difference is applied across its ends will be

• 5 : 4 : 3

• 6 : 3 : 2

• 4 : 3 : 2

• 6 : 4 : 3

Four identical cells of emf E and internal resistance r are to be connected in series. Suppose, if one of the cell is connected wrongly, the equivalent emf and effective internal resistance of the combination is

• 2E and 4r

• 4E and 4r

• 2E and 2r

• 4E and 2r

A parallel plate capacitor is charged and then isolated. The effect of increasing the plate separation on charge, potential and capacitance respectively are

• constant, decreases, increases

• constant, decreases, decreases

• constant, increases, decreases

• increases, decreases, decreases

24.

A spherical shell of radius 10 cm is carrying a charge q. If the electric potential at distances 5 cm, 10 cm and 15 cm from the centre of the spherical shell is V₁, V₂ and V₃ respectively, then

• V₁ = V₂ > V₃

• V₁ > V₂ > V₃

• V₁ = V₂ < V₃

• V₁ < V₂ < V₃

Three point charges 3 nC, 6 nC and 9 nC are placed at the corners of an equilateral triangle of side 0.1 m. The potential energy of the system is

• 991 μJ

• 8910 μJ

• 891 μJ

• 99100 μJ

In the circuit shown below, the ammeter and the voltmeter readings are 3A and 6V respectively. Then, the value of the resistance R is

• < 2 Ω

• 2 Ω

• ≥ 2 Ω

• > 2 Ω

Two cells of emf E₁ and E₂ are joined in opposition (such that E₁ > E₂). If r₁ and r₂ be the internal resistances and R be the external resistance, then the terminal potential difference is

• $\frac{{\mathrm{E}}_1 - {\mathrm{E}}_2}{{\mathrm{r}}_1 + {\mathrm{r}}_2} \times \mathrm{R}$

• $\frac{{\mathrm{E}}_1 + {\mathrm{E}}_2}{{\mathrm{r}}_1 + {\mathrm{r}}_2} \times \mathrm{R}$

• $\frac{{\mathrm{E}}_1 - {\mathrm{E}}_2}{{\mathrm{r}}_1 + {\mathrm{r}}_2 + \mathrm{R}} \times \mathrm{R}$

• $\frac{{\mathrm{E}}_1 + {\mathrm{E}}_2}{{\mathrm{r}}_1 + {\mathrm{r}}_2 + \mathrm{R}} \times \mathrm{R}$

A proton beam enters a magnetic field of 10^-4 Wb m^-2 normally. If the specific charge of the proton is 10¹¹ C kg^-1 and its velocity is 10⁹ ms^-1, then the radius of the circle described will be

• 100 m

• 0.1 m

• 1 m

• 10 m

Two concentric coils each of radius equal to 2 $\mathrm{\pi }$ cm are placed at right angles to each other. If 3A and 4A are the currents flowing through the two coils respectively. The magnetic induction (in Wb m^-2) at the centre of the coils will be

• 5 × 10^-5

• 12 × 10^-5

• 7 × 10^-5

• 10^-5

The resistance ofa bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance be 0.005 per°C, then its resistance will become 200 Ω at a temperature

• 500°C

• 300°C

• 200°C

• 400°C