Moving Charges and Magnetism — Physics STD 12 Science — Question

A thin convex lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in liquid of refractive index 4/3 , its focal length will be(a) 15 cm (b) 10 cm(c) 30 cm (d) 60 cm

According to Maxwell's hypothesis, changing of electric filed give rise to.

A beam of light propagating in medium A with index of refraction n (A) passes across an interface into medium B with index of refraction n(B). The angle of incidence is greater than the angle of refraction; v(A) and v(B) denotes the speed of light in A and B. Then which of the following is true (a) v(A) > v(B)  and n(A) > n(B)(b) v(A) > v(B)  and  n(A) < n(B)(c) v(A) < v(B)  and  n(A) > n(B)(d) v(A) < v(B)  and  n(A) < n(B)

The magnetic dipole moment of a current carrying coil does not depend upon:

Assertion   :  The resistance of super-conductor is zero.
Reason      : The super-conductors are used for the transmission of electric power.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

The potentials of the two plates of capacitor are +10V and –10 V. The charge on one of the plates is 40 C. The capacitance of the capacitor is(a) 2 F(b) 4 F(c) 0.5 F(d) 0.25 F

A rectangular block of glass ABCD has a refractive index 1.6. A pin is placed midway on the face AB (Fig). When observed from the face AD, the pin shall:

A river is flowing from west to east at a speed of 5 metres per minute. A man on the south bank of the river, capable of swimming at 10 metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction:

1. Due north.
2. 30° east of north.
3. 30° north of west.
4. 60° east of north.