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 ______.
  • $$\text{9000 kJ}$$
  • $$\text{9000 MJ}$$
  • $$\text{9 KJ}$$
  • $$\text{9 MJ}$$
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 $$v_P$$ and $$v_Q$$, then?
1163114_d089a82267a54d57b54c021b56e33699.png
  • $$v_P=v_Q$$
  • $$v_P < v_Q$$
  • $$v_P > v_Q$$
  • 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
  • $$\dfrac{nq}{(1-\sqrt n)^2}$$
  • $$\dfrac{-nq}{(1+\sqrt n)^3}$$
  • $$\dfrac{-nq}{(1+\sqrt n)^2}$$
  • $$\dfrac{q}{4}$$
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 
  • $$22 \omega$$ exact
  • $$22\pm 2.2\ \omega$$
  • $$\left(22\pm 4.4\right)\omega$$
  • $$22 \pm 0.44\ \omega$$
An electric heater rated as 2 kW is used to heat 200 kg of water from $$ 10^o C $$ to $$ 70^o C $$. Assuming no heat losses, the time taken is :
  • $$ 25.2 s $$
  • $$ 6 \times 10^3 s $$
  • $$ 25.2 \times 10^3 s $$
  • $$ 25.2 \times 10^6 s $$
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 $$\dfrac{a}{2}$$ and $$2a$$ respectively, from the axis of the wire is 
  • $$\dfrac{1}{4}$$
  • $$\dfrac{1}{2}$$
  • $$1$$
  • $$4$$
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 $$R_{1}=R_{3}and R_{2}=R_{4}$$
  • only $$R_{1}/R_{3}and R_{2}/R_{4}$$
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 $$220$$V. The wirng of the room consists of Cu of $$1$$mm radius and a length of $$10$$m. 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 and$$I = 2 sin \ \omega t$$ 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 $$5.0$$A to $$0.0$$A in $$0.1$$S. If an average emf of $$200$$V induced, given an estimate of the self-inductance of the circuit.
  • $$4$$H
  • $$40$$H
  • $$0.4$$H
  • $$0.04$$H
0:0:1


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