A charged particle moves in a circle in a uniform magnetic field. If its speed is doubled, what happens to the radius of its path?
Correct answer B. It doubles
Subject / 480 questions
MDCAT ECAT Physics MCQs
Page 11 of MDCAT ECAT Physics multiple-choice questions with answers. Tap an option to check yourself.
Page 11 of 24
- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
A proton travels at 1.0 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.10 T. Take mₚ = 1.67 × 10⁻²⁷ kg, e = 1.6 × 10⁻¹⁹ C. What is the radius of its circular path?
Correct answer B. 0.10 m
A metal coil has resistance 20 Ω at 20 °C and 24 Ω at 120 °C. Taking 20 °C as the reference, what is its temperature coefficient of resistance?
Correct answer C. 2.0 × 10⁻³ K⁻¹
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What is the SI unit of the temperature coefficient of resistance?
Correct answer A. K⁻¹
Which statement correctly describes a superconductor?
Correct answer A. Its resistance becomes zero below a critical temperature
When a cell supplies current to an external resistor, how does its terminal potential difference compare with its emf?
Correct answer B. It is less than the emf because of the voltage drop across the internal resistance
Under what condition is the terminal potential difference of a cell equal to its emf?
Correct answer D. When no current is drawn from the cell
A battery of emf 12 V and internal resistance 0.50 Ω is connected to a 5.5 Ω resistor. What is the potential difference across the battery terminals?
Correct answer A. 11 V
A battery of emf 9.0 V has a terminal potential difference of 7.5 V when it delivers 1.5 A. What is its internal resistance?
Correct answer C. 1.0 Ω
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What is the current when a cell of emf E and internal resistance r is short-circuited by a thick copper wire of negligible resistance?
Correct answer D. E/r
A cell has emf 1.5 V and internal resistance 0.25 Ω. What current flows if its terminals are joined by a wire of negligible resistance?
Correct answer A. 6.0 A
For a source of fixed emf and internal resistance r, the power delivered to an external load R is maximum when ____.
Correct answer B. R = r
A source has emf 12 V and internal resistance 2.0 Ω. What is the maximum power it can deliver to an external resistor?
Correct answer D. 18 W
When a source delivers maximum power to its external load, what is the efficiency of power transfer?
Correct answer A. 50%
A load resistor connected to a cell is increased from a value equal to the internal resistance to a much larger value. What happens to the efficiency of power transfer?
Correct answer C. It increases towards 100%
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In which direction does conventional current flow in the external part of a circuit connected to a cell?
Correct answer C. From the positive terminal to the negative terminal
A 20 Ω resistor carries a steady current of 0.30 A. What power is dissipated in it?
Correct answer D. 1.8 W
For an ohmic conductor at constant temperature, what does a graph of current against potential difference look like?
Correct answer C. A straight line through the origin with gradient 1/R
Two identical cells, each of emf 1.5 V and internal resistance 0.50 Ω, are connected in series with a 2.0 Ω resistor. What current flows?
Correct answer C. 1.0 A
Which change would increase the internal resistance of a simple electrolytic cell?
Correct answer A. Increasing the separation between its electrodes