Test: Electric Current (NCERT) - NEET MCQ

Here,number of electron,
n = 10000000 = 10⁷
Total charge on ten million electrons is
Q = ne [where e = 1.6 × 10⁻¹⁹C]
=10⁷ × 1.6 × 10⁻¹⁹C = 1.6 × 10⁻¹²C
Time taken by ten million electrons to pass from point P to point Q is
t = 1μs = 10⁻⁶s
The current
I = 
Since the direction of the current is always opposite to the direction of flow of electrons. Therefore due to flow of electrons from point P to point Q the current will flow from point Q to point P.

Q = It also Q = ne [e = 1.6 × 10⁻¹⁹C]
∴ ne = It or
= 6.25 × 10¹⁸ electrons s⁻¹

As I = dQ/dt ;
dQ − Idt ;
dQ = (2t² − 3t + 1)dt

Q.= 
= [2/5(125 − 27) − 32(25 − 9) + 2]
= 43.34C

Given:
I = 4 + 2t
Let dq be the charge which passes in a small interval of time dt. Then
dq = Idt
or dq = (4 + 2t) dt
On integrating, we get

= 48 C

Radius of electron orbit
r = 0.72Å = 0.72 × 10⁻¹⁰m
Frequency of revolution of electron in orbit of given atom
v = 9.4 × 10¹⁸ rev/s
(where T is time period of revolution of electron in orbit)
∴ Then equivalent current is
I = e/T = ev = 1.6 × 10⁻¹⁹ × 9.4 × 10¹⁸
= 1.504A