Electric Charges and Fields — Physics STD 12 Science — Question

Figure shows two capacitors connected in series and joined to a battery. The graph shows the variation in potential as one moves from left to right on the branch containing the capacitors:

1. C₁ > C₂
2. C₁ = C₂
3. C₁ < C₂
4. The information is not sufficient to decide the relation between C₁ and C₂.

Two wires of equal diameters, of resistivities  and   and lengths l₁ and l₂, respectively, are joined in series.  The equivalent resistivity of the combination is

(a)

(b)

(c)

(d)

A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because

The neutral temperature of a thermocouple is 350℃ when the cold junction is at 0℃ When the cold junction is immersed in a bath of 30℃, the inversion temperature is

(a) 700℃

(b) 600℃

(c) 350℃

(d) 670℃

Magnetic lines of force:

A thin lens focal length  and its aperture has diameter d. It forms an image of intensity I. Now the central part of the aperture upto diameter   is blocked by an opaque paper. The focal length and image intensity will change to

(a)  and

(b) f   and

(c)  and

(d) f   and

Ten grams of ⁵⁷Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly:

Two resistances are connected in two gaps of a metre bridge. The balance point is 20 cm from the zero end. A resistance of 15 ohms is connected in series with the smaller of the two. The null point shifts to 40 cm. The value of the smaller resistance in ohms is

(a) 3

(b) 6

(c) 9

(d) 12

In the network of resistors shown in the adjoining figure, the equivalent resistance between A and B is

(a) 54 ohm

(b) 18 ohm

(c) 36 ohm

(d) 9 ohm

An inductor, a resistance and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance: