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Questions >> JEEMAIN and NEET >> Physics

Physics

Which of these is correct for each pair of statements? \[\] Statement 1: When an electric current at the junction of two wires of the same material is directed from the thick wire to the thin wire, the drift speed of the electrons increase as they pass through the cross-section \[\] Statement 2: The drift speed of electrons is directly proportional to the electric field in the wire.

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A wire of resistance $10\Omega$ is bent to form a circle. $P$ and $Q$ are two points on it such that the arc $PQ$ subtends a right angle at the center. A $3V$ battery having internal resistance of $ 1\Omega$ is connected across $P$ and Q, the currents in the two parts of the circle are

asked Feb 10, 2014 by thanvigandhi_1

1 answer

Three resistances $ R, 2R$ and $3R$ are connected in parallel to a battery. Then

asked Feb 10, 2014 by thanvigandhi_1

1 answer

In a Hydrogen atom, an electron moves in an orbit of radius $5 \times 10^{-11}m$ with a speed of $2.2 \times 10^6 m/s.$ Calculate the equivalent current.

asked Feb 10, 2014 by thanvigandhi_1

1 answer

To get maximum current through a resistance of $2.5\Omega$, one can use $‘m’ $ rows of cells, each containing $‘n’$ cells connected in series. The internal resistance of each cell is $0.5\Omega$. What are the values of $ n$ and $m$ if the total numbers of cells are $45$?

asked Feb 10, 2014 by thanvigandhi_1

1 answer

Three concentric spherical metallic shells A , B and C of radii a ,b and c $\;(c > b> a)\;$ have charge densities $\;\sigma , - \sigma \;and\; \sigma\;$ respectively . The potential of shell B is

asked Feb 10, 2014 by yamini.v

1 answer

A battery of internal resistance $2 \Omega$ is connected to a variable resistor whose value can be varied from $ 4\Omega\: to\: 10\Omega$. If the variable resistance is gradually increased from an initial value of $4\Omega$, the power consumed by it:

asked Feb 10, 2014 by thanvigandhi_1

1 answer

How many electrons flow through the filament of a $120V, 60W $ bulb in one second?

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A current of $1A $ is passing through $ CuSO_4 $ solution. How many $Cu^{+2}ions$ ions will be deposited at the cathode in 5 seconds?

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A uniform wire has resistance $R$. It is cut into n equal parts and all of them are connected in parallel to each other. The resistance of the combination is:

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A battery is supplying power to a tape-recorder by cable of resistance $0.02\Omega$. If the battery is generating $50W $ at $5V$, the power received by the tape-recorder is:

asked Feb 10, 2014 by thanvigandhi_1

1 answer

Calculate the mean free path in $Cu$ at room temperature $300K$, if the number density of free electrons is $8.5 \times 10^{28}/m^3$ and resistivity $r = 1.7 \times 10^{-8} mho-m$. Given $k = 1.38 \times 10^{-23} J/K \: and\: 1A = 10^{-10} m$

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A capacitor is charged and then made to discharge through a resistance. The time constant is $ \tau$. In what time will the potential difference across the capacitor decrease by 10%

asked Feb 10, 2014 by thanvigandhi_1

1 answer

This question has statement I and statement II. Of the four choices given after the statements, choose the one that best describes the two statements.\[\] Statement- I: In a meter bridge experiment, the null point for the unknown resistance is measured. Now, the resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same point as before by decreasing the value of the standard resistance. \[\] Statement- II: Resistance of a metal increases with temperature.

asked Feb 10, 2014 by thanvigandhi_1

1 answer

A constant voltage is applied to the two ends of a uniform metallic wire. Some heat is produced in it. The heat developed is doubled if

asked Feb 8, 2014 by thanvigandhi_1

1 answer

This question has statement I and statement II. Of the four choices given after the statements, choose the one that best describes the two statements. \[\] Statement- I: Electrons in a conductor have no motion in the absence of a potential difference across it. \[\] Statement- II: The electric field inside the static conductor is always zero.

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Find the resistance of the wire frame shaped as a cube when measured between the points 1 and 3. The resistance of each edge is R

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Find the resistance of the wire frame shaped as a cube when measured between the points 1 and 2. The resistance of each edge is R

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Find the resistance of the wire frame shaped as a cube when measured between the points 1 and 7. The resistance of each edge is R

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Two capacitors $C_1$ and $C_2$ are charged to $120\: V$ and $ 200\: V$ respectively. It is found that by connecting them together the potential on each one can be made zero. Then:

asked Feb 8, 2014 by thanvigandhi_1

1 answer

This question has statement I and statement II. Of the four choices given after the statements, choose the one that best describes the two statements. \[\] Statement- I: Higher the range, greater is the resistance of ammeter. \[\] Statement- II: To increase the range of ammeter, additional shunt needs to be used across it.

asked Feb 8, 2014 by thanvigandhi_1

1 answer

The supply voltage to a room is $120\: V\: DC$. The resistance of the lead wires is $6 \Omega$. A $60\: W$ bulb is already switched on. What is the decrease of voltage across the bulb, when a $240\: W$ heater is switched on in parallel to the bulb?

asked Feb 8, 2014 by thanvigandhi_1

1 answer

In an $LCR$ circuit as shown below both switches are open initially. Now switch $S1$ is closed, $S2$ kept open. ($q$ is charge on the capacitor and $ \tau = RC$ is capacitive time constant). Which of the following statement is correct?

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are 3% each, then error in the value of resistance of the wire is

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Two electric bulbs marked $25W – 220V$ and $100W – 220V$ are connected in series to a $440V$ supply. Which of the bulbs will fuse?

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A resistance of $2 \Omega$ is connected across one gap of a meter-bridge and an unknown resistance, greater than $2 \Omega$, is connected across the other gap. When these resistances are interchanged, the balance point shifts by $20cm$. The unknown resistance is

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A moving coil galvanometer of resistance $100 \Omega$ is used as an ammeter using a resistance of $ 0.1 \Omega$. The maximum deflection current in the galvanometer is $100 \mu A$. Find the current in the circuit so that the ammeter shows full scale deflection

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A rigid container with thermally insulated walls contains a coil of $100 \Omega$ resistance with a current of $1A$. Change in internal energy after 5 min will be

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor are

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A capacitor $C_1$ of capacitance $1 \mu F$ and $C_2$ of capacitance $ 2 \mu F$ are separately charged by a common battery for a long time. The two capacitors are then separately discharged through equal resistors. Both the discharge circuits are connected at $t=0$. One or more of the following happen.

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A capacitor of capacitance $ 500 \mu F$ is connected to a battery through a $10k \Omega $resistor. Then, which of the following are true: \[\] The charge stored on the capacitor in the first $5s$ is larger than the charge stored in the next

asked Feb 8, 2014 by thanvigandhi_1

1 answer

A wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to the current, the temperature of the wire is raised by $ \Delta T$ in a time $t$. A number $N$ of similar cells are now connected in series with a wire of the same material and cross-section but of length $2L$. The temperature is raised by the same amount $ \Delta T$ in the same time. The value of $N$ is

asked Feb 8, 2014 by thanvigandhi_1

1 answer

In steady state, a resistor is carrying a current $i$. The power lost to the surroundings is $b(T- T_0)$. Here $b$ is a constant, $T$ is the temperature of the resistance and $T_0$ is the surrounding temperature. If the coefficient of linear expansion is $ \alpha$. The strain in the wire is

asked Feb 8, 2014 by thanvigandhi_1

1 answer

The length of the potentiometer wire is l. A cell of emf E is balanced at length $ \large\frac{l}{3}$ from the positive end of the wire. If the length of the wire is increased by $ \large\frac{l}{2}$, at what distance will the same cell give a balance point

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Two wires of resistivity $\rho 1$ and $ \rho 2$ are connected in parallel. Equivalent resistivity of the combination is

asked Feb 8, 2014 by thanvigandhi_1

1 answer

Initially the spheres A and B are at potential $\;V_{A}\;$ and $\;V_{B}\;$ respectively . Now sphere B is earthed by closing the switch . The potential of A will now become

asked Feb 7, 2014 by yamini.v

1 answer

A charged particle of mass m and charge q is released from rest from the position $\;(x_{0} ,0)\;$ in a uniform electric field $\;E_{0} \hat{j}\;.$ The angular momentum of particle about origin

asked Feb 7, 2014 by yamini.v

1 answer

An electric dipole is placed perpendicular to an infinite line of charge at some distance as shown in figure . Identify the correct statement

asked Feb 7, 2014 by yamini.v

1 answer

Potential due to a system at polar coordinates $\;(r , \theta)\;$ is given by $\;\large\frac{\alpha \;cos \theta}{r^2}\;$ Find the magnitude of electric field at that point if $\;\alpha=3 Vm^2\;,(r , \theta)=(\sqrt{3} ,tan^{-1} \large\frac{1}{\sqrt{2}}). $

asked Feb 7, 2014 by yamini.v

1 answer

Find potential difference $\;V_{AB}\;$ between $\;A(0,0,0)$ and $\;B(1m ,1m, 0)\;$ in an electric field $\;\overrightarrow{E}=y \hat{i}+x \hat{j}$

asked Feb 7, 2014 by yamini.v

1 answer

A uniform electric field exists in x -y plane. The potential of points $\;A (2m ,2m) , B (-2m ,2m)\;and\; C(2m ,4m)\;$ are 4V , 16V and 12V respectively . The electric field is

asked Feb 7, 2014 by yamini.v

1 answer

The electric field on the axis of a dipole of dipole moment $\;\overrightarrow{P}\;$ at a distance x from the line joining the charges and $\;(x > > d)\;$

asked Feb 7, 2014 by yamini.v

1 answer

There are four concentric shells A , B , C ,D of radii a , 2a ,3a and 4a respectively . Shells B and D are given charges +q and -q respectively . Shell C is now earthed . The potential difference $\;V_{A}-V_{C}\;$ is

asked Feb 7, 2014 by yamini.v

1 answer

If the electric potential of the inner shell is 10V and that of the outer shell is 5V , then the potential at the centre will be

asked Feb 7, 2014 by yamini.v

1 answer

Potential difference between centre and surface of the sphere of radius R and $\rho$ uniform volume charge density within it will be

asked Feb 7, 2014 by yamini.v

1 answer

Three concentric matallic shells A , B and C of radii R , 2R and 3R have surface charge densities $\;\sigma , -\sigma\;and\;\sigma\;$ respectively . Find the potential difference between A & C

asked Feb 7, 2014 by yamini.v

1 answer

Two concentric conducting spheres of radii R and 2R are carrying charges Q and -2Q respectively . If the charge on inner sphere is doubled the potential difference between the two spheres will becomes

asked Feb 7, 2014 by yamini.v

1 answer

Four point charges $\;+1 \mu C ,+1 \mu C,-1 \mu C-1 \mu C\;$ are placed at the four consecutive corners of a square of side 0.1m . What is the magnitude of electric field at E as shown in figure .

asked Feb 7, 2014 by yamini.v

1 answer

Two wires of resistivity $\rho 1$ and $\rho 2$ are connected in series. Equivalent resistivity of the combination is

asked Feb 6, 2014 by thanvigandhi_1

1 answer

A $4 \mu F$ capacitor and a 2.5MW resistor are connected in series with a 12V battery. Find the time after which the potential difference across the capacitor is 3 times the potential difference across the resistor.

asked Feb 6, 2014 by thanvigandhi_1

1 answer

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