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Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is one meter. A train is traveling with a velocity of 72 km/h along the track. The reading of the milli-voltmeter (in mV) is (Vertical component of the earth'smagnetic induction is 2 x 10-5 T)

A coil has 1,000 turns and 500cm2 as its area.The plane of the coil is placed at right angles to a magnetic induction field of 2x10-5web/m2.The coil is rotated through 1800 in 0.2 seconds.The average emf induced in the coil,in milli volts,is

A primary coil and secondary coil are placed close to each other. A current, which changes at the rate of 25 amp in a millisecond, is present in the primary coil. If the mutual inductance is 92x10-6 Henries,then the value of induced emf in the secondary coil is

A coil of 40H inductance is connected in series with a resistance of 8Ω and this combination is connected to the terminals of a 2V battery. The inductive time constant of the circuit is (in seconds)

In a coil of area 10cm2 and 10 turns with magnetic field directed perpendicular to the plane and is changing at the rate of 108 gauss/second.The resistance of the coil is 20Ω.The current in the coil will be

A coil has an inductance of 0.05H and 100 turns and 0.02A current is passed through it. Flux linked with coil is

A coil of 50 turns has dimension 10 x 10 cm. It is roated at the rate of 5 rps in a uniform magnetic field of flux density 0.7T. The maximum emf included in it is

A train is moving towards north with a speed of 180 kilometers per hour. If the vertical component of the earths magnetic field is 0.2x10-4T, the emf induced in the axle of length 1.5m is

An inductance 1 H is connected in series with an AC source of 220 V and 50 Hz. The inductive reactance (in ohm) is :

A coil has an inductance of 0.05H and 100 turns and 0.02A current is passed through it.Flux linked with coil is

A constant voltage of 25 V is applied to a series L-R circuit at t = 0, by closing a switch. What is the potential difference across the resistor and the inductor at time t = 0

A transformer steps up an A.C. voltage from 230V to 2300V. If the number of turns in the secondary coil is 1000, the number of turns in the primary coil will be

A small square loop of wire of side l is placed inside a large square loop of side L(L>>1). If the loops are coplanar and their centres coincide, the mutual induction of the system is directlv proportional to :

A long rigidly supported wire carries a current ia=96A.Directly above it and parallel to it at a distance,another wire of 0.144N weight per metre carrying a current ib=24A,in a direction opposite to that air due to magnetic repulsion,then its distance(in mm) from the lower wire is

The area of the coil in a moving coil galvanometer is 15cm2 and has 20 turns.The magnetic inductions is 0.2T and the couple per unit twist of the suspended wire is 10-6 Nm per degree.If the deflection is 450,the current passing through it is

A circular coil of radius 11cm,carries and current of 2.5 amperes.If it has 700 turns,the flux density at the centre of the coil is

The natural frequency of an I.-C circuit is 1,25,000 cycle/s. Then the capacitor C is replaced by another capacitor with a dielectric medium of dielectric constant K. In this case, the frequency decreases by 25 kHz. The value of K is

The current decays from 5A to 2A in 0.01s in a coil. The emf induced in a coil nearby it is 30V. The mutual inductance between the coils is

An ideal transformer has 400 turns in the primary and 200 turns in the secondary. If the primary connected to a 12V battery, then the secondary voltage is

A varying current in a coil changes from 10 A to zero in 0.5 seconds. If the average emf induced in the coil is 220 volts, the self-inductance of the coil is:

A step down transformer has a supply line voltage of 2200V in to 220V. The primary coil has 5000 turns. The efficiency and power transmitted by the transformer are 90% and 8 kilowatt respectively. Then the number of turns in the secondary is

The number of turns in primary and secondary coils of a transformer is 50 and 200. If the current in the primary coil is 4 A, then the current in the secondary coil is

An ideal transformer has 400turns in the primary and 200 turns in the secondary.If the primary is connected to a 12 V battery,then the secondary voltage is

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