Current Electricity by Rajeev Gupta (9013666301)

Charge through a cross-secion of a conductor is given by Q = 2 t² + 5 t) C. The curreny through the conductor at that instant t = 2 s would be

• 6.5 A

• 13 A

• 26 A

• zero

In a neon gas discharge tube 2.9 x 10¹⁸ Na⁺ ions move to the right through a cross-section of the tube while 1.2 x 10¹⁸ electrons to the left in this time. What would be the net current in the tube at the given time? (approx.) (charge on both type have 1.6 x 10^-19 C)

• 0.66 A

• 0.33 A

• 1.32 A

• 0.98 A

10⁹ electrons as well as positron are flowing normally through an area in forward and backward direction in the interval of 10 ms. The current through the area would be ( in pico-second)

• 16

• 32

• 8

• 24

In a Bohr model of hydrogen atom, the electron is assumed to rotate in a circular orbit of radius 5 x 10^-11 m, at a speed of 2.2 x 10⁶ m/s. The current associated with electron motion would be___ ( in mA)

• 2.24

• 1.12

• 3.26

• 4

If I₁, I₂ and I₃ are the orders of the currents through our nerves, domestic appliances and average lightening in cloud in rainy season, then the order of current would be

• I₁ > I₂ > I₃

• I₁ > I₃ > I₂

• I₁ < I₂ < I₃

• I₁ = I₂ = I₃

Masses of three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistance is

• 125 : 15 : 1

• 1 : 15 : 125

• 5 : 3 : 1

• 1 : 3 : 5

A potential difference V is applied to a conductor wire of length l and diameter d. How are the electric field E drift speed v_d and resistance R are affected if current I is doubled from earlier value?

• E is doubled, v_d is doubled and R is tripled

• E is halved, v_d is doubled and R remain the same

• E is halved, v_d is doubled and R is doubled

• E is halved, v_d is halved and R is doubled

The average drift speed of free electrons in a copper wire of area of cross-section 10^-7 m² carrying current of 1.5 A and having free electron density 8.5 x 10²⁸ /m³ will be

• 0.11 m/s

• 1.1 mm/s

• 2.2 mm/s

• 0.22 mm/s