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CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 9 - MCQExams.com

If a wire is stretched , so that its length is 20% more than its initial length, the percentage increase in the resistance of the wire is 
  • 40%
  • 10%
  • 44%
  • 25%
The electrical energy consumed by a 30 W bulb in 5 minutes is ______.
  • 9000 kJ
  • 9000 MJ
  • 9 KJ
  • 9 MJ
A wire has a non-uniform cross-section as shown in figure. A steady current flows through it. The drift speed of electrons at points P and Q is vP and vQ, then?
1163114_d089a82267a54d57b54c021b56e33699.png
  • vP=vQ
  • vP<vQ
  • vP>vQ
  • Data is insufficient
Two positive charges q and nq are placed on a straight line. A charge Q is placed at the neutral point so as to make the entire system in equilibrium. The charge Q is
  • nq(1n)2
  • nq(1+n)3
  • nq(1+n)2
  • q4
The post office box works on the principle of :
  • Potentiometer
  • Principle of wheat stone bridge
  • Matter waves
  • Ampere's law
The colour code on a resistor is red, red, black, the value of its resistance is 
  • 22ω exact
  • 22±2.2 ω
  • (22±4.4)ω
  • 22±0.44 ω
An electric heater rated as 2 kW is used to heat 200 kg of water from 10oC to 70oC. Assuming no heat losses, the time taken is :
  • 25.2s
  • 6×103s
  • 25.2×103s
  • 25.2×106s
A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross-section. The ratio o the magnetic fields B and B, at radial distances a2 and 2a respectively, from the axis of the wire is 
  • 14
  • 12
  • 1
  • 4
The Wheatstone bridge shown in the above figure is balanced. If the positions of the cell C and the galvanometer G are now interchanged, G will show zero deflection


1213370_6fff5dd29f814e82a6cf49952fd514db.PNG
  • in all cases
  • only if all the resistance are equal
  • only if R1=R3andR2=R4
  • only R1/R3andR2/R4
Find the value of I ?
1262224_fef66ced4e954cd29724477057bac443.png
  • -1.4 A
  • -2.1 A
  • 2 A
  • -4.2 A
When resistor are connected in series what remains same.?
  • Current
  • Voltage
  • Resistance
  • power
The magnetic field of 2\times { 10 }^{ 2 } T acts at right angles to a coil of area 100 cm^{2} with 50 turns. The average emf induced in the coil is 0.1 V, When it is removed from the field in time L.The value of t is
  • 0.1 s
  • 1 s
  • 0.01 s
  • 20 s
A room has AC run hours a day at a voltage of 220V. The wirng of the room consists of Cu of 1mm radius and a length of 10m. Power consumption per day is 10 commercial units . The fraction of it goes in the joule heating in wires is: \rho_{cu}=1.7\times10^{-8}\Omega m
  • 0.32\%
  • 0.2\%
  • 2\%
  • 3.2\%
If i=t^2 0 < t < T then r.m.s value of current is 
  • \dfrac {T^2} {\sqrt2}
  • \dfrac {T^2} {2}
  • \dfrac {T^2} {\sqrt5}
  • none of these
If the emf of the battery in primary circuit of a potetimeter is doubled the value of potential gradient will:-
  • Remain Uncharged
  • Be halved
  • Be doubled
  • None of these
Power dissipated in the circuit shown in  the figure 30 watt . The value of R is 
1270922_4bda86fdec8844658438ada515024106.png
  • 5 \Omega
  • 15 \Omega
  • 10 \Omega
  • 20 \Omega
All of the following can induce an emf in a coil of wire EXCEPT
  • moving a magnet through the coil
  • placing a stationary coil of wire in an increasing magnetic field
  • Placing a stationary coil of wire in a stationary magnetic field.
  • Placing a stationary coil of wire in a decreasing magnetic field.
To increase sensitivity of a potentiometer, its:
  • Area should be increase
  • Current should increase
  • length should increase
  • Current should decrease
Figure given below shows uniformly positively charged, thin rod of length L and four points A, B, C and D at the same distance d from the rod, with position as marked. If V_{A}, V_{B}, V_{C} and V_{D} are their respective potentials then.
1278688_8af589937c34406dbf01bd596c0db80c.jpg
  • V_{B} > V_{A} > V_{C} > V_{D}
  • V_{B} > V_{A} > V_{C} = V_{D}
  • V_{A} = V_{B} > V_{C} = V_{D}
  • V_{D} > V_{B} > V_{A} > V_{C}
For circuit shown, the value of emf of battery 'E' is.
1281416_200a866972d746d89f6699b0f452ece0.png
  • 15 V.
  • 8 v
  • 200v/7
  • 65v/7.
At what moment when the potentiometer is balanced ,
  • Current flows only in the primary circuit.
  • Current flows only in the secondary circuit.
  • current flows in both primary and secondary circuits .
  • current doesnot flow in any circuit
An electric bulb marked 40W-220V is connected with an electric supply of 110v. Its elctric power is
  • 100\ W
  • 40\ W
  • 20\ W
  • 10\ W
Potential difference across AB shown in the figure is:
1309413_8da9f45245714500b821613c51428d7c.png
  • 10 V
  • 12 V
  • 8 V
  • 0 V
See the diagram. Area of each plate is 2.0 m^2 and\  d = 2 \times 10^{-3} m A charge of 8.85 \times 10^{-8} C is given to Q. Then the potential of Q becomes :
1311059_73317b158d16477fae98befd500c823c.png
  • 13 V
  • 10 V
  • 66.7 V
  • 8.825 V
A 2V battery, a 990\Omega resistor and a potentiometer of 2m length, all are connected in series of the resistance of potentiometer wire is 10\Omega, then the potential gradient of the potentiometer wire is 
  • 0.05Vm^{-1}
  • 0.5Vm^{-1}
  • 0.01Vm^{-1}
  • 0.1Vm^{-1}
In a meter bridge setup, which of the following should be the properties of the one meter long wire?
  • High resistivity and low temperature coefficient
  • Low resistivity and low temperature coefficient
  • Low resistivity and high temperature coefficient
  • High resistivity and high temperature coefficient
\begin{array} { l } { \text { Two electric charges } 12 \mu C \text { and } - 6 \mu C } \ { \text { are placed } 20 \mathrm { cm } \text { apart in air.Net } }\\ { \text { electric field intensity at zero potential } } \ { \text { point on the line joining the charges } } \\ { \text { and outside the region between them } } \end{array}
  • 1.25 \times 10 ^ { 6 } N / C
  • 3.75 \times 10 ^ { 5 } N / C
  • 4.5 \times 10 ^ { 6 } N / C
  • 6.75 \times 10 ^ { 5 } N + C
Six identical cells, each of emf of 6V, are connected in parallel. The net emf across the battery is
  • 6V
  • 36V
  • 0V
  • Between 6V and 36V
Kirchoff's voltage law and current law are respectively in accordance with the conservation of 
  • Charge and momentum
  • Charge and energy
  • Energy and charge
  • Energy and momentum
For different values of resistance, R power consumption in R are given. Then which of the following values are not possible?
(a) 2W
(b) 5W
(c) 8W
(d) 4W
1300205_d556a2c50c084da4b1aaf98b0bfe5cff.PNG
  • Only c
  • b and c
  • a, b, c
  • All
In which of the cases no emf is induced in conducting wire?  
  • open circuit
  • conductor at rest
  • L perpendicular to B and v
  • None of the above
The figure shows three circuits I, II and III which are connected to a 3V battery. if the powers dissipated by the configurations I,II and III are P_1,P_2 and P_3 respectively, then :
1319415_ac0a1d474c834d2d803cd09db8da887d.PNG
  • P_1 > P_2 > P_3
  • P_1 > P_3 > P_2
  • P_2 > P_1 > P_3
  • P_3 > P_2 > P_1
 A capacitor C is connected to a battery of potential V. the distance between its plates is reduced to half, keeping the battery connected . then the work done by the battery is
  • \frac {CV^2}{4}
  • \frac {CV^2}{2}
  • \frac {3CV^2}{2}
  • CV^2
Terminal potential difference across the cell of emf 5v is:
1315202_00938ef4b89b4a1794ddda97939de9ba.PNG
  • V_a-V_b=10/3 V
  • V_a-V_b=5/3 V
  • V_a-V_b=5 V
  • V_a-V_b=8/3 V
Four charges +Q , -Q, +Q, -Q are placed at the corners of a square taken order. At the centre of the square :
  • E = 0, V = 0
  • E = 0, V \neq 0
  • E \neq 0, V = 0
  • E \neq 0, V \neq 0
An electric bulb is rated 220 V and 100 W . When it is operated om 110 V,the power consumed will be-
  • 100 W
  • 75 W
  • 50 W
  • 25 W
Which unit is not used in either the definition of the coulomb or the definition of the volt?
  • ampere
  • joule
  • ohm
  • second
When the switch S, in the circuit shown, is closed, then the value of current i will be :
1329657_24f2ea427d2246f6b0716a8748551b98.png
  • 3A
  • 5A
  • 4A
  • 2A
The magnitude and direction of current I (in A) indicated in the following circuit is
1356343_b70a59928fed4a50b45dcaa9cea7a223.png
  • 14 \rightarrow
  • 8 \rightarrow
  • \leftarrow 4
  • \leftarrow 6
Current l in the network shown in figure is :-
1363638_2a82d756757a4c708ac2a74e2c7aa3dc.png
  • 16 A
  • 3 A
  • 19 A
  • 12 A
In the situation shown, the currents through 3\Omega and 2\Omega resistances are in the ratio 
1371684_0abd401ed10c4ed1b1a9e30430799fad.png
  • 3:2
  • 7:4
  • 4:3
  • 3:1
Kirchhoff's junction law is equivalent to 
  • conservation of energy
  • conservation of charge
  • conservation of electric potential
  • conservation of electric flux
A cell of e.m.f. E is connected with an external resistance R; p.d. across the cell is v. the internal resistance of the cell will be:
  • ( E-V) R/E
  • ( E-V) R/V
  • (V-E)R/V
  • (V-E)R/E
A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively with and without being short circuited through a resistance of 10 \Omega Its internal resistance is -
  • 2.0 ohm
  • zero
  • 1.0 ohm
  • 0.5 ohm
In the given circuit diagram , the currents , { I }_{ 1 }=-0.3\quad A,{ I }_{ 4 }=0.8\quad A,and\quad { I }_{ 5 }=0.4\quad A, are flowing as shown . the currents { I }_{ 2 },{ I }_{ 3 }
1362953_7f38f722f818421cb02eccc019551298.png
  • 0.4 A, 1.1 A,0.4 A
  • 1.1 A, 0.4 A, 0.4 A
  • 1.1 A, -0.4 A, 0.4 A
  • -0.4 A, 0.4 A , 1.1 A
The peak value of an alternating e.m.f. which is given by E={ E }_{ 0 }\omega is 10 volts and its frequency is 50 Hz. At time t=\dfrac { 1 }{ 600 } s, The instantaneous e.m.f. 
  • 10 V
  • 5\sqrt { 3 } V
  • 5 V
  • 1 V
A potential gradient is created in the wire by standard cell for the comparision of emf's of two cells in a potentiometer experiment. Which possibility of the following will cause failure of the experiment. 
  • the emf of the standard cell is higher than that of the other cells.
  • the diameter of the wires is equal and similar,
  • 3) the number of wires is ten.
  • the emf of the standard cell is smaller than those of both the cells.
Four concentric spherical shell is A,B,C AND D has radius a, 2a, 3a  and 4a shell B and D has charge +q and-q.The shell 'C' is earthed. Find V_A - V_C
  • \dfrac{kq}{2a}
  • \dfrac{kq}{3a}
  • \dfrac{kq}{4a}
  • \dfrac{kq}{6a}
The potential difference V and the current I flowing an instrument in an ac circuit of frequency f are given by V = 5 cos \ \omega t volts andI = 2 sin \ \omega t amperes (where \omega= 2 \pi f). The power dissipated in the instrument is :-
  • Zero
  • 10 W
  • 5 W
  • 2.5 W
Current in a circuit falls from 5.0A to 0.0A in 0.1S. If an average emf of 200V induced, given an estimate of the self-inductance of the circuit.
  • 4H
  • 40H
  • 0.4H
  • 0.04H
0:0:1


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