Q. What is the focal length of a concave mirror if an object is placed at a distance of 30 cm from the mirror and the image is formed at a distance of 15 cm from the mirror?
A.
10 cm
B.
15 cm
C.
20 cm
D.
25 cm
Solution
Using the mirror formula, 1/f = 1/v + 1/u. Here, v = -15 cm (real image) and u = -30 cm (object distance). Thus, 1/f = 1/(-15) + 1/(-30) = -1/10, so f = -10 cm.
Q. What is the focal length of a concave mirror if an object placed at a distance of 30 cm produces an image at a distance of 10 cm? (2021)
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
Solution
Using the mirror formula, 1/f = 1/v + 1/u; here, v = -10 cm (real image) and u = -30 cm (object distance). Thus, 1/f = 1/(-10) + 1/(-30) = -1/6, so f = 5 cm.
Q. What is the focal length of a concave mirror if the object distance is 30 cm and the image distance is 15 cm? (2021)
A.
10 cm
B.
15 cm
C.
20 cm
D.
25 cm
Solution
Using the mirror formula, 1/f = 1/v + 1/u. Here, v = -15 cm (real image) and u = -30 cm (object distance). Thus, 1/f = 1/(-15) + 1/(-30) = -1/10, so f = -10 cm.
Q. What is the focal length of a concave mirror if the object is placed at a distance of 30 cm and the image is formed at a distance of 15 cm from the mirror? (2021)
A.
10 cm
B.
15 cm
C.
20 cm
D.
25 cm
Solution
Using the mirror formula, 1/f = 1/v + 1/u. Here, v = -15 cm (image distance is negative for concave mirror) and u = -30 cm. Therefore, 1/f = 1/(-15) + 1/(-30) = -1/10. Thus, f = 10 cm.
Q. What is the force experienced by a charge q moving with velocity v in a magnetic field B?
A.
qvB
B.
qvB sin(θ)
C.
qvB cos(θ)
D.
qvB tan(θ)
Solution
The force experienced by a charge q moving with velocity v in a magnetic field B is given by the Lorentz force law: F = q(v × B), which can be expressed as F = qvB sin(θ), where θ is the angle between the velocity and the magnetic field.
Q. What is the force experienced by a charge q moving with velocity v in a magnetic field B at an angle θ?
A.
qvB
B.
qvB sin(θ)
C.
qvB cos(θ)
D.
qvB tan(θ)
Solution
The magnetic force on a charge moving in a magnetic field is given by F = qvB sin(θ), where θ is the angle between the velocity and the magnetic field.
Q. What is the force experienced by a current-carrying conductor of length L in a magnetic field B at an angle θ? (2023)
A.
F = BIL
B.
F = BIL sin(θ)
C.
F = BIL cos(θ)
D.
F = BIL²
Solution
The force on a current-carrying conductor in a magnetic field is given by F = BIL sin(θ), where θ is the angle between the conductor and the magnetic field.
Q. What is the force on a charge moving in a magnetic field given by F = qvB sin(θ)? (2022)
A.
It is always zero
B.
It depends on the angle θ
C.
It is constant
D.
It is maximum when θ = 90°
Solution
The force on a charge moving in a magnetic field is maximum when the angle θ between the velocity vector and the magnetic field is 90°, as sin(90°) = 1.
Q. What is the force on a charge moving in a magnetic field given by the equation F = qvB sin(θ)? (2020)
A.
Charge times velocity
B.
Charge times magnetic field
C.
Charge times velocity times magnetic field times sine of angle
D.
Charge times sine of angle
Solution
The force on a charge moving in a magnetic field is given by F = qvB sin(θ), where q is the charge, v is the velocity, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field.
Correct Answer:
C
— Charge times velocity times magnetic field times sine of angle
