Current Electricity Practice Questions

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 $\rho$ (see figure). If the battery is connected to a resistance of value $\ {R},$ the maximum Joule heating in $\ {R}$ will take place for:-

A potentiometer wire ${PQ}$ of $1 {m}$ length is connected to a standard cell ${E}_{1} .$ Another cell ${E}_{2}$ of emf $1.02 {V}$ is connected with a resistance 'r' and switch $S$ (as shown in figure). With switch ${S}$ open, the null position isobtained at a distance of $49 {cm}$ from $\ {Q}$. The potential gradient in the potentiometer wire is :

A galvanometer having a coil resistan ce 100 Ω gives a full scale deflection when a current of 1 mA is passed through it. What is the value of the resistance which can convert this galvanometer into a voltmeter giving full scale deflection for a potential difference of 10 V?

Consider four conducting materials copper,tungsten, mercury and aluminium withresistivity $\rho _{ {C}}>\rho _{ {T}}>\rho _{ {M}}$ and$\rho _{ {A}}$ respectively. Then:

A 200Ω resistor has a certain color code. If one replaces the red color by green in the code, the new resistance will be :

In the circuit , the potential difference betweenA and B is :

Two electric bulbs, rated at (25 W, 220 V) and (100 W, 220 V), are connected in series across a 220 V voltage source. If the 25 W and 100 W bulbs draw powers $P_1$ and $P_2$ respectively, then:

A potentiometer wire AB having length L and resistance 12 r is joined to a cell D of emf ε and internal resistance r. A cell C having emf ε/2 and internal resistance 3r is connected. The length AJ at which the galvanometer as shown in fig. shows no deflectionis :

When the switch S, in the circuit shown, isclosed, then the value of current i will be : [9-Jan-2019 Shift 1]

A wire of resistance R is bent to form a square ABCD as shown in the figure. The effective resistance between E and C is: (E is mid-point of arm CD)

Two equal resistance when connected in series to a battery, consume electric power of 60 W. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be :

In a meter bridge, the wire of length 1 m has a non-uniform cross-section such that, the variation $\frac{dR}{dl}$ of its resistance R with length l is $\frac{dR}{dl}$ α $1/\text{sqrtl}$. Two equal resistances are connected as shown in the figure. The galvanometer haszero deflection when the jockey is at point P. What is the length AP?

A galvanometer of resistance 100 $\Omega$ has 50 divisions on its scale and has sensitivity of 20 $\muA$ / division. It is to be converted to a voltmeter with three ranges, of 0-2V, 0- 10 V and 0-20V. The appropriate circuit to do so is:

A galvanometer, whose resistance is 50 ohm, has 25 divisions in it. When a current of 4 × $10^{-4}$ A passes through it, its needle (pointer) deflects by one division. To use this galvanometer as a voltmeter of range 2.5 V, it should be connected to a resistanceof:

Space between two concentric conducting spheres of radii a and b (b>a) is filled with a medium of resistivity $\rho$.The resistance between the two spheres will be:

The Wheatstone bridge shown in Fig. here, gets balanced when the carbon resistor used as $R_1$ has the colour code ( Orange, Red, Brown). The resistors $R_2$ and $R_4$ are 80 Ω and 40 Ω respectively. Assuming that the colour code for the carbon resistors givestheir accurate values, the colour code for the carbon resistor, used as $R_3$ , would be :

a moving Coil galvanometer allows a full scale current $10^{-4}$ A.A series resistance of 2 MΩ is required to convert the above galvanometer into a voltmeter of range 0-5V. Therefore the value of shunt resistance required to convert the above galvanometer in to ammeter of range 0-10mA is :

A current of 5A passes through a copper conductor (resistivity= $1.7\times 10^{ -8}$Ωm) radius of cross section 5mm.Find the mobility of the charges if their drift velocity $1.1\times 10^{-3} {m} / {s}$