List of practice Questions

A battery, an open switch and a resistor are connected in series as shown in figure.

Consider the following three statements concerning the circuit. A voltmeter will read zero if it is connected across points (i) $P$ and $T$ (ii) $P$ and $Q$ (iii) $Q$ and $T$ Which one of the above is/are true ?

A battery has e.m.f. $4V$ and internal resistance $r$. When this battery is connected to an external resistance of $2\,\Omega $, a current of $1A$ flows in the circuit. How much current will flow if the terminals of the battery are connected directly

A battery of emf $15\, V$ and internal resistance of $4\,\Omega$ is connected to a resistor. If the current in the circuit is $2 \,A$ and the circuit is closed. Resistance of the resistor and terminal voltage of the battery will be

A car battery of e.m.f. $12 V$ and internal resistance $5 \times 10^{-2} \Omega$ receives a current of $60 A$ from an external source, then terminal potential difference of battery is :-

A cell of constant emf first connected to a resistance $ {{R}_{1}} $ and then connected to a resistance $ {{R}_{2}} $ . If power delivered in both cases is same, then the internal resistance of the cell is

A current in a wire is given by the equation, $I = 2t^2 - 3t + 1$, the charge through cross section of wire in time interval $t = 3\, s$ to $t = 5\,s$ is

A current of $5 \,A$ is passing through a metallic wire of cross-sectional area $ 4\times {{10}^{-6}}{{m}^{2}} $ . If the density of charge carriers of the wire is $ 5\times {{10}^{26}} $ $ {{m}^{-3}}, $ the drift velocity of the electrons will be

A galvanometer of $ 50\,\Omega $ resistance has $25$ divisions. A current of $ 4\times {{10}^{-4}} $ A gives a deflection of one division. To convert this galvanometer into a voltmeter having a range of $25\, V$, it should be connected with a resistance of

A galvanometer of resistance $20\, \Omega$ is to be converted into an ammeter of range $1\, A$. If a current of $1\, mA$ produces full scale deflection, the shunt required for the purpose is

A heater coil is cut into two equal parts and only one part is used in the heater, the heat generated becomes

A piece of wire of resistance 4 ohm is bent through 180 at its mid point and the two halves are twisted together. Then the resistance is

A potentiometer wire of length $100 \,cm$ has a resistance of $10 \,\Omega$. It is connected in series with a resistance and a cell of emf $2 \,V$ and of negligible internal resistance. A source of emf $10 \,mV$ is balanced against a length of $40 \,cm$ of the potentiometer wire. What is the value of external resistance ?

A sphere has surface charge density $\sigma$. It is surrounded by a spherical shell. The surface charge density on the spherical shell is

A voltmeter of resistance $R$ is to be used to measure the potential difference across a resistance $r$. The nearest reading in the absence of voltmeter ?

A wire of length $l$ and resistance $R$ is stretched to get the radius of cross-section $ \frac{r}{2} $ . Then the new value of $R$ is

According to the Kirchhoffs law the sum of the products of current and resistance as well as emfs in a closed loop is :

All of the following statements are true except

An ammeter, voltmeter and a resistor are connected in series to a cell and the readings are noted as $I$ and $V$ . If another resistor $R$ is connected in parallel with voltmeter, then

An electric bulb rated 220V, 100W is connected to a source of 220 (0.8)V then actual power will be

An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be

An electric lamp is marked 100 W, 220 V. If it operates at 200 V, the current through it will be:

An electric motor runs on DC source of emf $200 \,V$ and draws a current of $10\, A$. If the efficiency be $40\%$, then the resistance of armature is

An electron moves in a circle of radius $1.0 \,cm$ with a constant speed of $ 4.0\times {{10}^{6}}m/s $ , the electric current at a point on the circle will be $ (e=1.6\times {{10}^{-19}}C) $

At room temperature, copper has free electron density of $8.4 \, \times \, 10^{28} \, m^{- 3}$ . The electron drift velocity in a copper conductor of cross-sectional area $10^{- 6} \, m^{2}$ and carrying a current of $5.4 \, A$ , will be -

Calculate the steadystate current in the $2\,\Omega$ resistor shown in the circuit in the figure.

The internal resistance of the battery is negligible and the capacitance of the condenser $C$ is $0.2\, \mu F$.