# 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 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