MCQOPTIONS
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MCQOPTIONS
This section includes 39 Mcqs, each offering curated multiple-choice questions to sharpen your Physics knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
When a bar magnet falls through a long hollow metal cylinder fixed with its axis vertical, the final acceleration of the magnet is [BVP 2003] |
| A. | Equal to zero |
| B. | Less than g |
| C. | 4 |
| D. | Equal to g in to beginning and then more than g |
| Answer» B. Less than g | |
| 2. |
In the diagram shown if a bar magnet is moved along the common axis of two single turn coils A and B in the direction of arrow [Kerala (Engg.) 2001] |
| A. | Current is induced only in A & not in B |
| B. | Induced currents in A & B are in the same direction |
| C. | Remains unchanged |
| D. | Induced currents in A & B are in opposite directions |
| Answer» E. | |
| 3. |
Lenz?s law applies to [DCE 1999] |
| A. | Electrostatics |
| B. | Lenses |
| C. | \[\frac{q}{2{{\varepsilon }_{0}}A}\] |
| D. | Cinema slides |
| Answer» D. Cinema slides | |
| 4. |
To induce an e.m.f. in a coil, the linking magnetic flux [KCET 1994] |
| A. | Must decrease |
| B. | Can either increase or decrease |
| C. | \[0.025\,Joule\] |
| D. | Must increase |
| Answer» C. \[0.025\,Joule\] | |
| 5. |
The dimensions of magnetic flux are [MP PMT 1994; CBSE PMT 1999] |
| A. | \[ML{{T}^{-2}}{{A}^{-2}}\] |
| B. | \[M{{L}^{2}}{{T}^{-2}}{{A}^{-2}}\] |
| C. | \[\frac{Q}{A{{\varepsilon }_{0}}}\left( \frac{{{k}_{1}}}{{{t}_{1}}}+\frac{{{k}_{2}}}{{{t}_{2}}} \right)\] |
| D. | \[M{{L}^{2}}{{T}^{-2}}{{A}^{-1}}\] |
| Answer» E. | |
| 6. |
A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field, the pendulum will |
| A. | Keep oscillating with the old time period |
| B. | Keep oscillating with a smaller time period |
| C. | \[2qC\] |
| D. | Come to rest very soon |
| Answer» E. | |
| 7. |
Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increasing with time. The induced current in the inner loop then, is [MP PET 1993] |
| A. | Clockwise |
| B. | Zero |
| C. | 477 \[m\] |
| D. | In a direction that depends on the ratio of the loop radii |
| Answer» D. In a direction that depends on the ratio of the loop radii | |
| 8. |
Lenz's law is consequence of the law of conservation of [JIPMER 1997; CPMT 1990; RPMT 1997; MP PET 1999; MP PMT 2000, 03; RPET 2003; AFMC 2004] |
| A. | Charge |
| B. | Momentum |
| C. | Equal on both |
| D. | Energy |
| Answer» E. | |
| 9. |
In a coil of area \[10\ c{{m}^{2}}\] and 10 turns with a magnetic field directed perpendicular to the plane and is changing at the rate of \[{{10}^{8}}\]gauss/second. The resistance of the coil is 20 ohm. The current in the coil will be [CPMT 1976] |
| A. | 5 amp |
| B. | 0.5 amp |
| C. | Farad/m |
| D. | \[5\times {{10}^{8}}\ amp\] |
| Answer» B. 0.5 amp | |
| 10. |
A 50 turns circular coil has a radius of \[3\ cm\], it is kept in a magnetic field acting normal to the area of the coil. The magnetic field \[B\] increased from 0.10 tesla to 0.35 tesla in 2 milliseconds. The average induced e.m.f. in the coil is [MP PET 1994] |
| A. | \[1.77\ volts\] |
| B. | \[17.7\ volts\] |
| C. | \[5cm\] |
| D. | \[0.177\ volts\] |
| Answer» C. \[5cm\] | |
| 11. |
At a place the value of horizontal component of the earth's magnetic field H is \[3\times {{10}^{-5}}\,Weber/{{m}^{2}}\]. A metallic rod AB of length 2 m placed in east-west direction, having the end A towards east, falls vertically downward with a constant velocity of 50 m/s. Which end of the rod becomes positively charged and what is the value of induced potential difference between the two ends [MP PET 1996] |
| A. | End A, \[3\times {{10}^{-3}}\,mV\] |
| B. | End A, 3 mV |
| C. | \[9\times {{10}^{-9}}\] |
| D. | End B, 3 mV |
| Answer» C. \[9\times {{10}^{-9}}\] | |
| 12. |
A 50 volt potential difference is suddenly applied to a coil with \[L=5\times {{10}^{-3}}\] henry and \[R=180\,ohm\]. The rate of increase of current after 0.001 second is [MP PET 1994] |
| A. | 27.3 amp/sec |
| B. | 27.8 amp/sec |
| C. | \[C{{V}^{2}}\] |
| D. | None of the above |
| Answer» E. | |
| 13. |
A conducting rod AC of length 4l is rotated about a point O in a uniform magnetic field \[\vec{B}\] directed into the paper. AO = l and OC = 3l. Then |
| A. | \[{{V}_{A}}-{{V}_{O}}=\frac{B\omega {{l}^{2}}}{2}\] |
| B. | \[{{V}_{O}}-{{V}_{C}}=\frac{7}{2}B\omega {{l}^{2}}\] |
| C. | 4C |
| D. | \[{{V}_{C}}-{{V}_{O}}=\frac{9}{2}B\omega {{l}^{2}}\] |
| Answer» D. \[{{V}_{C}}-{{V}_{O}}=\frac{9}{2}B\omega {{l}^{2}}\] | |
| 14. |
Plane figures made of thin wires of resistance R = 50 milli ohm/metre are located in a uniform magnetic field perpendicular into the plane of the figures and which decrease at the rate dB/dt = 0.1 m T/s. Then currents in the inner and outer boundary are. (The inner radius a = 10 cm and outer radius b = 20 cm) |
| A. | 10? 4 A (Clockwise), 2 ´ 10? 4 A (Clockwise) |
| B. | 10? 4 A (Anticlockwise), 2 ´ 10? 4 A (Clockwise) |
| C. | \[4C\] |
| D. | 2 ´ 10? 4 A (Anticlockwise), 10? 4 A (Anticlockwise) |
| Answer» B. 10? 4 A (Anticlockwise), 2 ´ 10? 4 A (Clockwise) | |
| 15. |
The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is 10W. The current in the circuit will be now |
| A. | i = 0.5 A |
| B. | i > 0.5 A |
| C. | \[\frac{{{q}^{2}}}{2{{\varepsilon }_{0}}A}\] |
| D. | i = 0 |
| Answer» C. \[\frac{{{q}^{2}}}{2{{\varepsilon }_{0}}A}\] | |
| 16. |
As shown in the figure a metal rod makes contact and complete the circuit. The circuit is perpendicular to the magnetic field with \[B=0.15\,tesla.\] If the resistance is \[3\,\Omega \], force needed to move the rod as indicated with a constant speed of \[2m/sec\] is [MP PET 1994] |
| A. | \[3.75\times {{10}^{-3}}\]N |
| B. | \[3.75\times {{10}^{-2}}\,N\] |
| C. | Nature of the material |
| D. | \[3.75\times {{10}^{-4}}N\] |
| Answer» B. \[3.75\times {{10}^{-2}}\,N\] | |
| 17. |
A copper rod of length l is rotated about one end perpendicular to the magnetic field B with constant angular velocity \[\omega \]. The induced e.m.f. between the two ends is [MP PMT 1992; Orissa JEE 2003] |
| A. | \[\frac{1}{2}B\omega {{l}^{2}}\] |
| B. | \[\frac{3}{4}B\omega {{l}^{2}}\] |
| C. | \[26.6\mu \,F\] |
| D. | \[2B\omega {{l}^{2}}\] |
| Answer» B. \[\frac{3}{4}B\omega {{l}^{2}}\] | |
| 18. |
Assertion : Self-inductance is called the inertia of electricity. Reason : Self-inductance is the phenomenon, according to which an opposing induced e.m.f. is produced in a coil as a result of change in current or magnetic flux linked in the coil. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | Remain constant |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» C. Remain constant | |
| 19. |
Assertion : Faraday?s laws are consequences of conservation of energy. Reason : In a purely resistive ac circuit, the current lags behind the e.m.f. in phase. [AIIMS 2002] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | Charge on the \[25\ cm\] sphere will be greater than that on the \[20\ cm\] sphere |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» D. If the assertion and reason both are false. | |
| 20. |
Assertion : A metal piece and a non-metal (stone) piece are dropped from the same height near earth?s surface. Both will reach the earth?s surface simultaneously. Reason : There is no effect of earth?s magnetic field on freely falling body. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | \[1.8\times {{10}^{-5}}m\] |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» E. If assertion is false but reason is true. | |
| 21. |
Assertion : Lenz?s law violates the principle of conservation of energy. Reason : Induced e.m.f., opposes always the change in magnetic flux responsible for its production. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» F. | |
| 22. |
In an inductor of inductance L = 100 mH, a current of \[I=10A\] is flowing. The energy stored in the inductor is [Orissa PMT 2004] |
| A. | 5 J |
| B. | 10 J |
| C. | If assertion is true but reason is false. |
| D. | 1000 J |
| Answer» B. 10 J | |
| 23. |
Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to [MP PET 2001] |
| A. | Heating effect of current alone |
| B. | Hysteresis loss alone |
| C. | If assertion is true but reason is false. |
| D. | None of the above |
| Answer» D. None of the above | |
| 24. |
In a step-up transformer the turn ratio is 1:10. A resistance of 200 ohm connected across the secondary is drawing a current of 0.5 A. What is the primary voltage and current [MP PET 2000] |
| A. | 50 V, 1 amp |
| B. | 10 V, 5 amp |
| C. | Equal to g |
| D. | 20 V, 2 amp |
| Answer» C. Equal to g | |
| 25. |
Which of the following is not an application of eddy currents [CBSE PMT 1989] |
| A. | Induction furnace |
| B. | Galvanometer damping |
| C. | Current is induced only in B and not in A |
| D. | X-ray crystallography |
| Answer» E. | |
| 26. |
The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of [CBSE PMT 1997; AIIMS 1999] |
| A. | 200 V, 50 Hz |
| B. | 2 V, 50 Hz |
| C. | Electro-magnetic induction |
| D. | 2 V, 5 Hz |
| Answer» B. 2 V, 50 Hz | |
| 27. |
In a transformer the primary has 500 turns and secondary has 50 turns. 100 volts are applied to the primary coil, the voltage developed in the secondary will be [MP PMT 1997] |
| A. | 1 V |
| B. | 10 V |
| C. | Must remain constant |
| D. | 10000 V |
| Answer» C. Must remain constant | |
| 28. |
A step up transformer connected to a 220 V AC line is to supply 22 kV for a neon sign in secondary circuit. In primary circuit a fuse wire is connected which is to blow when the current in the secondary circuit exceeds 10 mA. The turn ratio of the transformer is [MP PET 1997] |
| A. | 50 |
| B. | 100 |
| C. | \[M{{L}^{2}}{{T}^{-1}}{{A}^{-2}}\] |
| D. | 200 |
| Answer» C. \[M{{L}^{2}}{{T}^{-1}}{{A}^{-2}}\] | |
| 29. |
The alternating voltage induced in the secondary coil of a transformer is mainly due to [MP PET 1992; MP PMT 1996] |
| A. | A varying electric field |
| B. | A varying magnetic field |
| C. | Keep oscillating with a larger time period |
| D. | The iron core of the transformer |
| Answer» C. Keep oscillating with a larger time period | |
| 30. |
A step-down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is 20 : 1. If transformer efficiency is 100%, then the current flowing in primary coil will be [MP PMT 1991] |
| A. | 1600 A |
| B. | 20 A |
| C. | Counter clockwise |
| D. | 1.5 A |
| Answer» D. 1.5 A | |
| 31. |
In a transformer 220 ac voltage is increased to 2200 volts. If the number of turns in the secondary are 2000, then the number of turns in the primary will be [MP PET/PMT 1988] |
| A. | 200 |
| B. | 100 |
| C. | Mass |
| D. | 20 |
| Answer» B. 100 | |
| 32. |
What is increased in step-down transformer [MP PMT/PET 1998; CPMT 1999] |
| A. | Voltage |
| B. | Current |
| C. | 0.05 amp |
| D. | Current density |
| Answer» C. 0.05 amp | |
| 33. |
A transformer is employed to [MP PET 1985; MP PMT 1993; RPET 1999] |
| A. | Obtain a suitable dc voltage |
| B. | Convert dc into ac |
| C. | \[177\ volts\] |
| D. | Convert ac into dc |
| Answer» D. Convert ac into dc | |
| 34. |
An electric motor operates on a 50 volt supply and a current of 12A. If the efficiency of the motor is 30%, what is the resistance of the winding of the motor [Kerala PET 2002] |
| A. | \[6\Omega \] |
| B. | \[4\Omega \] |
| C. | End B, \[3\times {{10}^{-3}}\,mV\] |
| D. | \[3.1\Omega \] |
| Answer» D. \[3.1\Omega \] | |
| 35. |
In a dc motor, induced e.m.f. will be maximum [RPMT 1997] |
| A. | When motor takes maximum speed |
| B. | When motor starts rotating |
| C. | 2.73 amp/sec |
| D. | When motor is switched off |
| Answer» B. When motor starts rotating | |
| 36. |
Armature current in dc motor will be maximum when [CPMT 1986, 88; MP PET 1995] |
| A. | Motor has acquired maximum speed |
| B. | Motor has acquired intermediate speed |
| C. | \[{{V}_{A}}-{{V}_{C}}=4B\omega {{l}^{2}}\] |
| D. | Motor is switched off |
| Answer» D. Motor is switched off | |
| 37. |
The output of a dynamo using a splitting commutator is |
| A. | dc |
| B. | ac |
| C. | 2 ´ 10? 4 A (clockwise), 10? 4 A (Anticlockwise) |
| D. | Half-wave rectified voltage |
| Answer» D. Half-wave rectified voltage | |
| 38. |
If rotational velocity of a dynamo armature is doubled, then induced e.m.f. will become [MP PMT 1991; AIIMS 2000] |
| A. | Half |
| B. | Two times |
| C. | i < 0.5 A |
| D. | Unchanged |
| Answer» C. i < 0.5 A | |
| 39. |
Which of the following does not depend upon the magnetic effect of some sort |
| A. | Moving coil galvanometer |
| B. | Hot wire ammeter |
| C. | \[3.75\times {{10}^{2}}\,N\] |
| D. | Electric motor |
| Answer» C. \[3.75\times {{10}^{2}}\,N\] | |