Wave Optics — Physics STD 12 Science — Question

A galvanometer of resistance 20 W is to be converted into an ammeter of range 1 A.  If a current of 1 mA produces full scale deflection, the shunt required for the purpose is

(a) 0.01 W

(b) 0.05 W

(c) 0.02 W

(d) 0.04 W

The electric potential at a point on the axis of an electric dipole depends on the distance r of the point from the dipole as

(a) ∝

(b) ∝

(c) ∝ r

(d) ∝

A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100Ω. He finds the null point at l₁ = 2.9cm. He is told to attempt to improve the accuracy. Which of the following is a useful way?

Three charges each of magnitude q are placed at the corners of an equilateral triangle, the electrostatic force on the charge placed at the center is (each side of triangle is L)

(a) Zero

(b)

(c)

(d)

Emission spectrum of CO₂​ gas:

Assertion  :   The electric bulbs glows immediately when switch is on.

Reason      : The drift velocity of electrons in a metallic wire is very high.

(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.

When a PN junction diode is reverse biased

(a) Electrons and holes are attracted towards each other and move towards the depletion region

(b) Electrons and holes move away from the junction depletion region

(c) Height of the potential barrier decreases

(d) No change in the current takes place

The continuous x-ray spectrum obtained from a Coolidge tube is of the form

(a)

(b)

(b)

(d)