Current Electricity

During an experiment with a metre bridge, the galvanometer shows a null point when the jockey is pressed at 40.0 cm using a standard resistance of 90 Ω, as shown in the figure. The least count of the scale used in the metre bridge is 1 mm. The unknown resistance is

In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW. The voltage of the electric mains is 220 V. The minimum capacity of the main fuse of the building will be :

A d.c. main supply of e.m.f. 220 V is connected across a storage battery of e.m.f. 200 V through a resistance of 1 Ω. The battery terminals are connected to an external resistance 'R'. The minimum value of 'R', so that a current passes through the battery to charge it is :

In the circuit shown, current (in A) through the 50 V and 30 V batteries are, respectively :

The circuit shown here has two batteries of 8.0 V and 16.0 V and three resistors 3 Ω, 9 Ω and 9 Ω and a capacitor 5.0 μF.

How much is the current I in the circuit in steady state ?

In the experiment of calibration of voltmeter, a standard cell of e.m.f. 1.1 volt is balanced against 440 cm of potentiometer wire. The potential difference across the ends of resistance is found to balance against 220 cm of the wire. The corresponding reading of voltmeter is 0.5 volt. The error in the reading of voltmeter will be :

Four bulbs $B_1$, $B_2$, $B_3$ and $B_4$ of 100 W each are connected to 220 V main as shown in the figure. The reading in an ideal ammeter will be :

If the direct transmission method with a cable of resistance $0.4\ \Omega\,\mathrm{km^{-1}}$ is used, the power dissipation (in %) during transmission is

For the resistance network shown in the figure, choose the correct option(s).

A meter bridge is set-up as shown, to determine an unknown resistance 'X' using a standard 10 ohm resistor. The galvanometer shows null point when tapping-key is at 52 cm mark. The end-corrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of 'X' is

Two batteries of different emfs and different internal resistances are connected as shown. The voltage across AB in volts is

Consider a thin square sheet of side L and thickness t, made of a material of resistivity $\rho$. The resistance between two opposite faces, shown by the shaded areas in the figure is

Incandescent bulbs are designed by keeping in mind that the resistance of their filament increases with the increase in temperature. If at room temperature, 100 W, 60 W and 40 W bulbs have filament resistances $R_{100}$, $R_{60}$ and $R_{40}$, respectively, the relation between these resistances is

To verify Ohm's law, a student is provided with a test resistor $R_T$, a high resistance $R_1$, a small resistance $R_2$, two identical galvanometers $G_1$ and $G_2$, and a variable voltage source V. The correct circuit to carry out the experiment is

In the graphs below, the resistance R of a superconductor is shown as a function of its temperature T for two different magnetic fields $B_1$ (solid line) and $B_2$ (dashed line). If $B_2$ is larger than $B_1$, which of the following graphs shows the correct variation of R with T in these fields?

A superconductor has $T_c(0)=100$ K. When a magnetic field of 7.5 Tesla is applied, its $T_c$ decreases to 75 K. For this material one can definitely say that when

When two identical batteries of internal resistance 1Ω each are connected in series across a resistor R, the rate of heat produced in R is $J_1$. When the same batteries are connected in parallel across R, the rate is $J_2$. If $J_1=2.25J_2$ then the value of R in Ω is

You are given many resistances, capacitors and inductors. These are connected to a variable DC voltage source (the first two circuits) or an AC voltage source of 50 Hz frequency (the next three circuits) in different ways as shown in Column II. When a current $I$ (steady state for DC or rms for AC) flows through the circuit, the corresponding voltage $V_1$ and $V_2$ (indicated in circuits) are related as shown in Column I. Match the two.

For the circuit shown in the figure

Figure shows three resistor configurations R1, R2 and R3 connected to 3 V battery. If the power dissipated by the configuration R1, R2 and R3 is P1, P2 and P3, respectively, then