Current at all points of a series circuit must be the same, because there's no place in the circuit where electrons are being manufactured, and no place where they're leaking out and falling on the floor. The nimber of electrons that leaves the loop is the same number that entered it.
I'm not sure what is nmeant by "p.d. remains different" .
Answer:
A. 20 N
Explanation:
Weight of the book = mass × acceleration due to gravity
= 2 × 10
= 20 N
Answer: 430 nm.
Explanation:
The relation of wavelength and frequency is:
Formula used :
where,
= frequency =
= wavelength = ?
c = speed of light = 
Now put all the given values in this formula, we get

Thus the wavelength (in nm) of the blue light emitted by a mercury lamp is 430 nm.
437 is the answer for that