# Physics Ch 3 Class 12 Electromagnetism

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Unit of Magnetic Flux is

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In CRO, electrons are emitted from:

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A 3-cm length of wire is moved at right angles across a uniform magnetic field with a speed of 2.0 m/s . If the flux density is 5.0 teslas, what is the magnitude of the induced e.m.f?

NTS 2016 DUHS & JSMU
Physics
Magnetism and Electromagnetic Induction
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A coil of 600 turns is threaded by a flux of 8×10-5 webers if this flux is reduced to 3×10-5 webers in 0.015 seconds. The average induced e.m.f. is:

NTS 2011
Physics
Magnetism and Electromagnetic Induction
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In transmission from grid station, power losses are minimized by:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
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How fast an H+ ion should move in magnetic field 2.5×10-3 T such that magnetic force equal its weight?

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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Transformer works on the principle of:

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
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What are dimensions of Magnetic Flux

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Due to the magnetic force, a positively charged particle executes uniform circular motion within a uniform magnetic field ‘B’. If the charge is ‘q’ and radius of its path is r, which of the expressions gives the magnitude of the particle’s linear momentum:

NTS 2010
Physics
Magnetism and Electromagnetic Induction
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Four particles independently move at the same speed in a direction perpendicular to the same magnetic field. Which particle is deflected the most?

NTS 2017
Physics
Magnetism and Electromagnetic Induction
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Moving charge produce field

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Two parallel straight conductors, in which current is flowing in the same direction, attract each other. The cause of it is:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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A circuit in which there is a current of 10 amperes is changed so that the current falls to zero in 0.5 seconds. If an average e.m.f. of 400 volts is induced, what is the self-inductance of the circuit?

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
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Magnetic force on a moving charge depends upon:

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
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If current passing through a solenoid is increased, which of the following must increase:

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the value of permeability

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The current measuring part of the Avometer consists of a number of low resistors connected …

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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By changing the current through the same coil, an emf is induced in it, the process is known as:

NTS 2015 SMBBMC
Physics
Magnetism and Electromagnetic Induction
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If the current in the wire is directed into the page, and the wire is held perpendicular to the page, then the direction of magnetic circles will be:

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The direction of the magnetic line of force depends upon:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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A force which is experienced in a magnetic field depends on:

NTS 2011
Physics
Magnetism and Electromagnetic Induction
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F = I L B, What Is relation between I and L

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A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1kV, its kinetic energy will be:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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If a wire having current 10A has a 3T magnetic field, what will be the magnetic field at a point from the wire at double the distance?

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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The SI unit of magnetic flux is Weber which is equivalent to:

NUMS 2019 Reconduct
Physics
Magnetism and Electromagnetic Induction
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If the length of a current carrying solenoid is doubled keeping the number of turns same and the current is increased to 9 times, the value of magnetic field compared to the original magnetic field B will be:

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If a stationary bar magnet is placed near a coil so that maximum lines of force passes through the coil, the galvanometer shows:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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In a certain circuit, a transistor has a collector current of 10mA and a base current of 40μA. What is the current gain of the transistor?

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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When a transformer is connected to 120-volt ac, it supplies 3000 V to a device. The current through the secondary winding then is o.06 A and the current through the primary is 2 A. The number of turns in the primary winding is 400. The number of turns in the secondary winding is:

NTS 2016 DUHS & JSMU
Physics
Magnetism and Electromagnetic Induction
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In a coil, when current changes from 10 A to 4 A in 1 s. An induced emf of 1.2 V is induced across the coil. The self – inductance of the coil is:

NUMS 2019 Cancelled
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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Transformer is a device which steps up or steps down the input:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
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A conductor of length L is moved across a magnetic field. Due to this activity, a potential difference appears across the ends of the conductor. This type of potential difference is termed as:

NTS 2018
Physics
Magnetism and Electromagnetic Induction
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Two point charges of +5 C and -12 C attract each other with a force of 1.48 N. charge of -5 C is added to each of these charges. Now the force will be:

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
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A particle of charge -0.04C is projected with speed 2 x 104 m/s into a uniform magnetic field ‘B’ of strength 0.5 T. If the particle’s velocity as it enters the field is perpendicular to ‘B’, what is the magnitude of the magnetic force on this particle:

NTS 2010
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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A circuit in which there is a current of 5 amp is changed so that the current falls to zero in 0.1s. If an average e.m.f of 200 volts is induced, what is the self-inductance of the circuit?

NTS 2014
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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A current carrying conductor is lying perpendicular to magnetic field and experiencing some force. If the conductor rotates by 60 degrees counter clock wise, the force on it will

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A 3-cm length of wire is moved at right angles across a uniform magnetic field with a speed of 2.0 m/s . If the flux density is 5.0 teslas, what is the magnitude of the induced e.m.f?

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

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A magnetic needle is placed in a uniform magnetic field and is aligned with the field. The needle is now rotated by an angle of 60 degrees and work done is W. The torque on the magnetic needle at this position is

NUMS 2014
Physics
Magnetism and Electromagnetic Induction
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EEG is related to:

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If a constant current is flowing through a coil, then the flux through that coil will become constant. In such types of arrangements, the electromotive force (emf) induced in the coil will be:

NTS 2018
Physics
Magnetism and Electromagnetic Induction
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Identify the instrument/s which is/are used for the measurement of resistance:

I. Wheatstone Bridge

II. Meter Bridge

III. Post office Box

IV. Ohmmeter

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
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An electron is moving along the axis of a solenoid carrying a current. Which of the following is a correct statement about the electromagnetic force acting on the electron?

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
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If electron passes through axis of solenoid the movement will be:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
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