Showing 91–100 of 207 questions
A current-carrying conductor is placed in a magnetic field perpendicular to it. What force acts on it?
A
Gravitational force
B
Lorentz force
C
Electrostatic force
D
Frictional force
Correct Answer:
B. Lorentz force
Explanation:
The force on a current-carrying conductor in a magnetic field is called the Lorentz force, given by F = BIL
What is the angle of incidence when light ray falls on a plane mirror and the angle of reflection is 35°?
Explanation:
According to law of reflection, angle of incidence equals angle of reflection
A transformer has 500 turns in primary and 100 turns in secondary coil. If primary voltage is 220V, what is the secondary voltage?
A
44 V
B
1100 V
C
22 V
D
110 V
Explanation:
Using transformer equation Vs/Vp = Ns/Np, we get Vs = 220 × (100/500) = 44 V
Which phenomenon explains the formation of a rainbow?
A
Refraction and dispersion
B
Reflection only
C
Diffraction only
D
Interference only
Correct Answer:
A. Refraction and dispersion
Explanation:
Rainbows form due to refraction of sunlight entering water droplets and dispersion of different wavelengths
An object is placed 30 cm in front of a concave mirror with focal length 10 cm. Where is the image formed?
A
15 cm behind the mirror
B
15 cm in front of the mirror
C
20 cm in front of the mirror
D
20 cm behind the mirror
Correct Answer:
A. 15 cm behind the mirror
Explanation:
Using mirror formula 1/f = 1/u + 1/v, where f = -10 cm, u = -30 cm, we get v = -15 cm (behind mirror)
A lens has a focal length of 15 cm. What is its power?
A
+6.67 D
B
-6.67 D
C
+2.25 D
D
-2.25 D
Correct Answer:
A. +6.67 D
Explanation:
Power P = 1/f (in meters). P = 1/0.15 = 6.67 Diopters (positive for converging lens)
What is the SI unit of pressure?
A
Bar
B
Pascal
C
Atm
D
Torr
Correct Answer:
B. Pascal
Explanation:
Pascal (Pa) is the SI unit of pressure, equal to 1 N/m²
A car moving at 20 m/s suddenly applies brakes with deceleration of 5 m/s². How far does it travel before stopping?
A
20 m
B
40 m
C
60 m
D
80 m
Explanation:
Using v² = u² + 2as, where v = 0, u = 20 m/s, a = -5 m/s². We get s = 400/10 = 40 m
Which of the following is NOT a SI base unit?
A
Ampere
B
Kelvin
C
Newton
D
Mole
Correct Answer:
C. Newton
Explanation:
Newton is a derived unit (kg⋅m⋅s⁻²). Ampere, Kelvin, and Mole are SI base units
A body is thrown vertically upward with a velocity of 40 m/s. What is the maximum height reached? (Take g = 10 m/s²)
A
80 m
B
40 m
C
160 m
D
120 m
Explanation:
Using v² = u² - 2gh, where final velocity v = 0, u = 40 m/s, g = 10 m/s². We get h = 1600/20 = 80 m
