# Competitive Exams: Physics MCQs (Practice_Test 2 of 35)

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When a charged particle is under the influence of a magnetic field, the path of its motion will be

a circle

along the lines of force

a parabola

a helix

A potentiometer is more appropriate for measuring potential difference than a voltmeter because

the sensitivity of a potentiometer is higher than that of a voltmeter

the resistance of potentiometer wire is very low

the potentiometer does not draw any current from the unknown source of emf

the resistance of the voltmeter is high

Consider the following statements regarding the network shown in the above figure:

The equivalent resistance of the network between points A and B is independent of the value of R'

The equivalent resistance of the network between points A and B is 4/3 R.

The current flowing through R'is zero.

Which of the above statement (s) is/are correct?

1 alone

2 alone

2 and 3

1, 2 and 3

A galvanometer has a resistance of 1000 R. It gives full scale deflection with 0.2 mA. If it is converted into an ammeter to measure 2A, then the value of the shunt resistance's' required is

0.1

10

100

105

The production of absorption of heat by the passage of an electric current through the junctions of two dissimilar metals is called

Thomson effect

Seeback effect

Peltier effect

Joule heating effect

Consider the following statements with regard to two metal strips of a thermocouple:

Free electron density is different in different metals.

Free electron density in a metal depends on temperature

Thomson effect in a thermocouple occurs

due to both 1 and 2

due to 2 but not due to 1

due to 1 but not due to 2

neither due to 1 nor due to 2

A proton of energy 1 MeV moves in a uniform magnetic field along a circular path. The energy for an? -particle to circulate along the same orbit in the same magnetic field is:

1 MeV

2 MeV

3 MeV

4 MeV

A rectangular coil having 60 turns with dimensions of 10 cm x 20 cm is set rotating at a constant speed of 1400 rpm in a uniform magnetic field of flux density B = 0.5 Wb/m2. If the axis of the coil is perpendicular to the field, then the maximum emf produced is

110 V

88 V

44 V

28 V

The value of current in the armature of a do motor is maximum when the motor

starts rotating

has gained full speed

starts rotating with mean speed

is switched off

The distance between the ends of the wings of an aeroplane is 3 m. This aeroplane is descending with a speed of 300 km/hour. If the horizontal component of earth's magnetic field is 0.4 Gauss, then the value of emf induced in the wings of the plane will be

2 V

1 V

0.1 V

0.01 V

The magnetic moment of a circular orbit of radius ‘r’ carrying a charge ‘q’ and rotating with velocity ‘v’ is given by

qvr/27?

qvr/2

q v? r

q v? r2

If R, X and Z represent, respectively, the resistance, reactance and impedance of an electric circuit carrying ac, then the power factor of the circuit is given by

R/Z

Z/R

R/X

X./R

If the frequency is 60 Hz. Then the capacitance of a capacitor, which must be connected in series with a resistance of 5? and inductance of 200 mH to bring the current in phase with voltage will be

30.2? F

32? F

35.2? F

40.4? F

If E is an electric field and B is the magnetic induction, then the energy flow per unit area per unit time in an electromagnetic field is given by

E x B

E. B

E2 + B2

E/B

The magnetisation (M) of a paramagnetic substance is proportional to external magnetic field strength (B) and temperature (T). If C = Curie constant, then the correct relationship among M, B and T is

M = C B

M = C T T2 B

M = C BT

M = C B T