If four identical resistors, of resistance 8 ohm, are first connected in series so as to give an effective resistance R_s, and then connected in parallel so as to give an effective resistance R_p then the ratio $\dfrac{R$s}{Rp} is

1. 32
2. 2
3. 0.5
4. 16

Assertion (A) : The colour of aqueous solution of copper sulphate turns colourless when a piece of lead is added to it.

Reason (R) : Lead is more reactive than copper, and hence displaces copper from its salt solution.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.

In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have

1. higher power ratings such as geyser.
2. lower power ratings such as fan.
3. metallic bodies and low power ratings.
4. non-metallic bodies and low power ratings.

The resultant magnetic field at point 'P' situated midway between two parallel wires (placed horizontally) each carrying a steady current I is

1. in the same direction as the current in the wires.
2. in the vertically upward direction.
3. zero
4. in the vertically downward direction.