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CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 8 - MCQExams.com

The supply voltage to a room is 120 V. The resistance of the lead wires is 6 Ω. A 60W,120V bulb is already switched on. What is the decrease of voltage across the bulb, when a 240W,120V heater is switched on in parallel to the bulb?
  • 2.9 volt
  • 13.3 volt
  • 10.04 volt
  • zero volt
A 220 volt, 1000 watt bulb is connected across a 110 volt mains supply. The power consumed will be.
  • 750 watt
  • 500 watt
  • 250 watt
  • 1000 watt
The resistance of a 10m long potentiometer wire is 50Ω. It is connected in series with a 3V battery and 10Ω resistor. The potential difference between two points separated by distance 40cm is equal to ______
  • 0.02V
  • 0.1V
  • 0.06V
  • 1.2V
If the figure shows a part of an electric circuit, then the current I is
1016741_6b588bda42de45c4bde49b47b2332494.PNG
  • 1A
  • 3A
  • 2A
  • 4A
If i1=3sinωt and i2=4cosωt, then i3 is -
1021440_60f5b332b2ee4a11a4500ea0432a5ce5.png
  • 5sin(ωt+53o)
  • 5sin(ωt+37o)
  • 5sin(ωt+45o)
  • 5cos(ωt+53o)
A solid spherical conducting shell has inner radius a and outer radius 2a. At the centre of the shell a point charge +Q is located. What must be the charge of the shell be in order for the charge density on the inner and outer surfaces of the shell to be exactly equal?
1026888_f6e3330c09964e12b1a591640cc085e8.png
  • 5Q
  • +3Q
  • 4Q
  • +4Q

Consider a cube as shown in the fig-1; with uniformly distributed charge within its volume. The potential at one of its vertex P is V0.A cubical portion of half the size (half edge length) of the original cube is cut and removed as shown in the fig-Find the modulus of potential at the point P in the new structure. 


1026679_89861f650228459494da9b7c7bf6693b.png
  • 78V0
  • V02
  • 3V04
  • V04
The number of turns in th coil of an ac generator is 5000 and the area of the coil is 0.25 m2. The coil is rotated at the rate of 100 cycles/s in a magnetic field of 0.2 T. The peak value of emf generated is nearly:
  • 786 kV
  • 440 kV
  • 220 kV
  • 157.1 kV

A potentiometer has a wire of 100 cm length and its resistance is 10 ohms. It is connected in series with a resistance of 40 ohms and a battery of emf 2 V  and negligible internal resistance. If a source of  unknown emf E connected in the secondary is balanced by 40 cm length of potentiometer wire, the value of E is:

  • 0.2 V
  • 0.4 V
  • 0.08 V
  • 0.16 V
Refer to teh circuit shown. What will be the total power dissipation in the circuit if P is the power dissipated in R1? It is given that R2=4R1 and R3=12R1
1028158_9490e31283ea4eb58a741eee56a3ca02.png
  • 4P
  • 7P
  • 13P
  • 17P
A potentiometer wire of 10 m length and having a resistance of 1 ohm/m is connected to an accumulator of emf 2.2 volt and a high resistance box. To obtain a potential gradient of 2.2mV/m, the value of resistance used from the resistance box is :-
  • 790 ohm
  • 810 ohm
  • 990 ohm
  • 1000 ohm
The temperature coefficient of resistance of wire is 12.5×104/C0. At 300K the resistance of the wire is 1 ohm. The temperature at which resistance will be 2 ohm is
  • 1154K
  • 1100K
  • 1400K
  • 1127K

For the following circuits, the potential difference between
X and Y in volt is (VxVy)


1043163_8009f5fd84634aafa5efb62cb3ffc698.png
  • 1
  • -1
  • 2
  • -2
Write T against true and F against false in the statements.
A charged glass road attract a charged plastic straw
  • True
  • False
If current I1=3A sin ωt and I2=4A cos ωt, then I3 is :
1046047_91e72dfeae304255ab578b157cc36a73.png
  • 5Asin(ωt+530)
  • 5Asin(ωt+370)
  • 5Asin(ωt+450)
  • 5Asin(ωt+300)
 In the circuit shown, the current in the 1ohm resistor is:
1036746_d8aa134d30fb46f5977a3b563757529c.png
  • 0.13A, from Q to P
  • 0.13A, from P to Q
  • 1.3A, from P to Q
  • 0A,
In the diagram shown P is a point negative charge. It's weight is balanced by the electric force due to the fixed very long wire. The equilibrium of the particle is
1063098_3ac4799f160841b396ec705bed667edb.png
  • Stable for vertical displacements
  • Neutral for vertical displacements
  • Stable for horizontal displacements (parallel to the wire)
  • Neutral for horizontal displacements (parallel to the wire)
Find the potentials of points A and B:-
1066581_e88bd68347b5405aa5c47a199c425099.png
  • VA=+10 V;VB=0 V
  • VA=+7.5 V;VB=2.5 V
  • VA=+2.5 V;VB=7.5 V
  • VA=+0 V;VB=10 V
If the resistance in the circuit is increased four times by keeping the potential difference the same, the current in the circuit is ___________.
  • Remains same
  • Four times
  • One fourth
  • Half
AB is part of a circuit as shown, that absorbs energy at a rate of 50 W. E is an electromotive force device that has no internal resistance.
1087383_52b5727ee0fb4984bc0c9879b84b95e1.JPG
  • Potential difference across AB is 48V
  • Electromotive force device is 48V.
  • Point B is connected to the positive terminal of E.
  • Rat of conversion from electrical to chemical energy is 48W in device E.
Charges 25Q,9Q and Q are placed at point ABC such that AB=4m, BC=3m and angle between AB and BC is 90. then force on the charge C is:
  • Zero
  • q2π05
  • 2Q2π0
  • 5Q24π0
The VI graph for a conductor at temperature T1 and T2 are as shown in figure. The term (T2T1) is proportional to:
1079367_95d8343e4307445f8b93cbc8616ec65e.png
  • cos2θ
  • sin2θ
  • cot2θ
  • tan2θ
An electric motor operates on a 50 V supply and a current of 1 A. If the efficiency of the motion is 30 %, what is the resistance of winding of motion ?
  • 35 Ω
  • 4 Ω
  • 2.9 Ω
  • 3.1 Ω
Potentiometer wire Pq of length 1m is connected to a standard cell E1 Another cell of E2 of emf1.02v/s connected as shown in the circuit diagram with a resistance 'r' and with a switch 's' . With the switch  S open, null position is obtained at a distance of 51 cm from p,Calculate
  • emf of the cell.
  • Potential gradient of the wire.
  • When switch S is closed, will null point moves towards p or Q?
  • insufficient data
Potentiometer is based on
  • Deflection method
  • Zero deflection method
  • Both (a) and (b)
  • None of these
Two cells each of electromotive force E and internal resistance r are concerned in parallel across the resistance R. The maximum energy given to the resistor per second if:
  • R=r2
  • R=r
  • R=2r
  • R=0
The wire of potentiometer has resistance 4Ω and length 1m. It is connected to a coil of electromotive force 2 volt and internal resistance 1Ω. If a cell of electromotive force 1.2 volt is balanced by it, the balancing length will be:
  • 90 cm
  • 60 cm
  • 50 cm
  • 75 cm
For comparing the electromotive force of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wire. Which of the following possibilities would make the experiment unsuccessful?
  • The electromotive force system of the standard cell is larger than the E electromotive force system of the two cells.
  • The diameter of the wires is the same and uniform throughout
  • The number of wires is ten
  • The electromotive force of the standard cell is smaller than the electromotive force of the two cells.
Two identical batteries, each of electromotive force 2V and internal resistance r=1Ω are connected as shown. The maximum power that can be developed across R using these batteries is:
1098583_b293159296b249398ac22236b72b7aa2.png
  • 2W
  • 3.2W
  • 8,2W
  • 4W
n identical cells each of electromotive force e and internal resistance r are connected in series of this combination. The current through V is:
  • 2en
  • n enR+r
  • eR+nr
  • n eR+r
A resistor of resistance 1000Ω is connected to an AC source E=220Vsin(100πrad/s . the power consumed by resistor is
  • 48.4W
  • 24.2W
  • 12.1W
  • ZERO
For an AC Circuit, the potential difference and current are given by V=102sinωt (inV) and I=22cosωt (in A) respectively.The power dissipated in the instrument is:
  • 20W
  • 40W
  • 402W
  • Zero
Eight resistances each of resistance 5Ω are connected in the circuit as shown in figure. The equivalent resistance between A and B is
1113134_1cdebc466273425eb0e244de5d046333.png
  • 83Ω
  • 163Ω
  • 157Ω
  • 192Ω
Two resistances of 400Ω and 800Ω are connected in series with a 6 volt battery of negligible internal resistance. A voltmeter of resistance 10,000Ω is used to measure the potential difference across 400Ω. The error in the measurement of the potential difference in volts approximately is :
  • 0.01
  • 0.02
  • 0.03
  • 0.05
If i1=3sinωtandi2=4cosωt, then i3 is
1121363_dcdbdb64e95c488a901a2994868c64e9.PNG
  • 5sin(ωt+53)
  • 5sin(ωt+37)
  • 5sin(ωt+45)
  • 5cos(ωt53)
In wheatstone's bridge P=9 ohm, R=4 ohm and S=6 ohm. How much resistance must be put in parallel to the resistance S to balance the bridge?
  • 24 ohm
  • 13.5 ohm
  • 7.2 ohm
  • 18.7 ohm

A circular coil of area 8m2  and number of turns 20 is placed in a magnetic field of 2T with its plane perpendicular to it. It is rotated with an angular velocity of 20rev/s about its natural axis. The emf induced is

  • 400V
  • 800πV
  • Zero
  • 400πV
In the following diagram, the deflection in the galvanometer in a potentiometer
circuit is zero, then 

1145121_d08ac4852753413caa6ea6d7a9e82ef2.png
  • E1>E2
  • E2>E1
  • E1=E2
  • E1+E2=E
At what  temperature will the resistance of a copper wire become three times its value at 00 C? [Temperature coefficient of resistance for copper = 4×103per0C]:-
  • 5000C
  • 4500C
  • 6000C
  • None of these
Taking the electric charge 'e' and permittivity ϵ .use dimensional analysis to determine the correct expression for Wp. Where Wp angular frequency N number of density of free electron, m mass
  • Nemϵ
  • meNϵ
  • Ne2mϵ
  • Ne3mϵ
Wattless current in the circuit is
1126927_0b059c0a9219440c978d8383ea4b13d0.png
  • 3.75 A
  • 5 A
  • 2.1 A
  • zero
Three resistances R1,R2 & R3 (R1>R2>R3) are connected in series. If current I1,I2 & I3 respectively is flowing through them, the correct relation will be
  • I1=I2=I3
  • I1>I2>I3
  • I1<I2<I3
  • I1>I2<I3
The inductance of a coil is L=10H and resistance R=5Ω. If applied voltage of battery is 10V and it switches off in 1 millisecond, find induced electromotive force of inductor.
  • 2×104V
  • 1.2×104V
  • 2×104V
  • None of these
If the circuit shown in the figure, the internal resistance of the battery is 1.5Ω and Vp and VQ are potentials at P and Q respectively. What is the potential difference between the points P and Q
1138408_1b85dcbdf72a4349bd73c533d5a3ced0.png
  • Zero
  • 4 volt (Vp>VQ)
  • 4 volt (VQ>VP)
  • 2.5 volt (VQ>VP)
In the given figure, if the heat flowing through the 5 ohm resistance is 10 calorie then how much heat is flowing through the 4 ohm resistance ?
1126595_ad43ea590f614b86a8256bf284a4f71d.png
  • 1 calorie
  • 2 calorie
  • 3 calorie
  • 4 calorie
An electron is rotating around an infinite positive linear charge in a circle of radius 0.1 m, if the linear charge density is 1μC/m, then the velocity of electron in m/s will be
  • 0.562×107
  • 5.62×107
  • 562×107
  • 0.0562×107
A 3hp motors requires 2.4kw to drive it; its efficiency is about:
  • 90%
  • 75%
  • 60%
  • 50%
For which of the following substances the resistance decreases with the decrease in temperature:
  • Germanium
  • Silicon
  • Silver
  • None
The temperature coefficient of resistance of a wire is 0.00125 per degree celcius. At 300 K its resistance of the wire is 2 ohms. The temperature when resistance doubles is :-
  • 1154 K
  • 1100 K
  • 600 K
  • 1400 K
The name of the instrument which records electrical energy consumed by customer is
  • Ampere-hour meter
  • Watt-hour meter
  • Var-hour meter
  • Volt-ampere meter
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Practice Class 12 Medical Physics Quiz Questions and Answers