Nuclei — Physics STD 12 Science — Question

A 100 W bulb B₁, and two 60-W bulbs B₂ and B₃, are connected to a 250 V source, as shown in the figure. Now W₁, W₂ and W₃ are the output powers of the bulbs B₁, B₂ and B₃, respectively. Then

(a)

(b)

(c)

(d)

The dimensions of electric flux are:

Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is

(a) 2 : 1

(b) 1 : 2

(c) 4 : 1

(d) 1 : 4

The sensitivity of a tangent galvanometer can be increased by increasing:

A magnetic field can be produced by:

An alternating current generator has an internal resistance R_g and an internal reactance X_g. It is used to supply power to a passive load consisting of a resistance R_g and a reactance X_L. For maximum power to be delivered from the generator to the load, the value of X_L is equal to:

Three observers A, B and C measure the speed of light coming from a source to be  and . The observer A moves towards the source, the observer C moves away from the source with the same speed. The observer B stays stationary. the surrounding space is vacuum every where. Then

(a)

(b)

(c)

(d)

Assertion     :   If the distance between parallel plates of a capacitor is halved and dielectric constant is made three times, then the capacitor becomes 6 times.

Reason        : Capacity of the capacitor does not depend upon the nature of the material.

(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.

Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is: