Overview

A wire carrying current I is bent in the shape ABCDEFA as shown, where rectangles ABCDA and ADEFA are perpendicular to each other. If the sides of the rectangles are of lengths a and b, then the magnitude and direction of magnetic moment of the loop ABCDEFA is:

Model a torch battery of length l to be made up of a thin cylindrical bar of radius 'a' and a concentric thin cylindrical shell of radius 'b' filled in between with an electrolyte of resistivity ρ (see figure). If the battery is connected to a resistance of value R, the maximum joule heating in R will take place for:

Consider four conducting materials copper, tungsten, mercury and aluminum with resistivity ρc, ρt, ρm and ρa respectively. Then

A galvanometer is used in laboratory for detecting the null point in electrical experiments. If, on passing a current of 6 mA it produces a deflection of 2°, its figure of merit is close to:

The balancing length for a cell is $560\mathrm{c}\mathrm{m}$ in a potentiometer experiment. When an external resistance of $10\mathrm{\Omega }$ is connected in parallel to the cell, the balancing length changes by $60\mathrm{c}\mathrm{m}$ . If the internal resistance of the cell is $\frac{N}{10}\mathrm{\Omega }$ , where $N$ is an integer then value of $N$  is

The length of a potentiometer wire is $1200\mathrm{c}\mathrm{m}$ $$ and it carries a current of $$ $60\mathrm{m}\mathrm{A}$ . For a cell of emf $5\mathrm{V}$ $$ and internal resistance of $20\mathrm{\Omega }$ $$ , the null point on it is found to be at $1000\mathrm{c}\mathrm{m}$ $$ . The resistance of whole wire is:

The current $I_1$ ${}_{}$ (in A) flowing through $$ $1\mathrm{\Omega }$ resistor in the following circuit is

In a building there are 15 bulbs of $45\mathrm{W},15$ bulbs of $100\mathrm{W},15$ small fans of $10\mathrm{W}$ and 2 heaters of $1\mathrm{k}\mathrm{W}$ . The voltage of electric main is $220\mathrm{V}$ . The minimum fuse capacity (rated value) of the building will be

In the figure given, the electric current flowing through the 5 k Ω resistor is ‘x’ mA. The value of x to the nearest integer is --------.

A resistor develops 500J of thermal energy in 20 s when a current of 1.5A is passed through it. If the current is increased from 1.5 A to 3 A, what will be the energy developed in 20 s.