Higher Study | Physics | Electromagnetic Oscillations and Alternating Current

What is the function of a transformer?

ক

Transformer is used to step down or up the AC voltages and currents

খ

Transformer is used to step down or up the DC voltages and currents

গ

Transformer converts DC to AC voltages

ঘ

Transformer converts AC to DC voltages

Choose the incorrect statement

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An action for slander cannot be brought jointly against several defendants

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In libel each person is liable for the entire publication, and therefore all may be properly sued together

গ

If several persons are libeled by the publication of a statement all of them cannot bring joint action against the defendant but must sue him separately

ঘ

An action for slander can be brought jointly against several defendants

In an AC circuit with resistance R and oscillating potential v = vm sinωt, the average current over a cycle is

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\(\frac {v_m }{R}\)

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\(0.637 \frac {v_m }{R}\)

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\(0.707 \frac {v_m }{R}\)

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zero

The transformer core is laminated in order to

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Simplify its construction

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Minimize eddy current loss

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Reduce cost

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Reduce Hysteresis loss

ঙ

none of the above

An LCR circuit is connected to AC voltage source V. If VR, VC and VL are the voltage drops across resistance, capacitor and inductor respectively, then V is expressed as:

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V = VR + VC + VL

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V = (VR + VC + VL)2

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V = [VR2 + (VL - VC)2]1/2

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V = [VR + (VL - VC)]1/2

If the value of capacitance is halved and that of resistance and inductance is doubled in an LCR circuit, the new impedance of the circuit will be

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increased by 4 times

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decreased by 4 times

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is halved

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increased by two times

In an LCR circuit, the value of capacitance is halved and that of resistance and inductance is doubled. The new impedance of the circuit is

ক

increased by two times

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decreased by 4 times

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is halved

ঘ

remains unchanged

Step-up transformer is used to increase the:

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D.C. potential difference

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D.C. resistance

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A.C. potential difference

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A.C. reactance

Core of a transformer is made of:

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soft iron

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copper

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Gold

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cobalt steel

Core of a transformer is made of

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Steel

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Cobalt steel

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Copper

ঘ

Soft iron

Working principle of transformer is

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Faraday's law

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Newtons law

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Avagadro's law

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stefan's law

For the given circuit the reading of voltmeter V and ammeter A is

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800V, 2 A

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300V, 2 A

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220V, 2.2A

ঘ

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The values of voltage and frequency of electric supply for domestic use in India are:

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220 V (r.m.s), 60 Hz.

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220 V (r.m.s), 50 Hz

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220 V (r.m.s), 100 Hz

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220 V (r.m.s), 80 Hz.

In a secondary coil of a step up transformer:

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less turns of thin wire

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more turns of thin wire

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less turns of thick wire

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more turns of thick wire

Work of invertor is:

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to change A.C. into D.C.

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to change D.C. to A.C.

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to regulate voltage

ঘ

none of these