Physics Current Electricity

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

In the circuit, given in the figure currents in different branches and value of one resistor are shown. Then potential at point B with respect to the point A is:

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:

Four resistances of $15\mathrm{\Omega },12\mathrm{\Omega },4\mathrm{\Omega }$ $$ and $$ $10\mathrm{\Omega }$ respectively in cyclic order to form Whetstone's network. The resistance that is to be connected in parallel with the resistance of $10\mathrm{\Omega }$  to balance the network is

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