Exams › JEE Main › Physics

Two wires of equal cross-sectional radius r but made of different materials are joined end to end (in series) and carry the same current. If the number densities of charge carriers in the two wires are in the ratio 1: 4, what is the ratio of the drift velocities of electrons in the two wires?

1. 4: 1
2. 1: 4
3. 2: 1
4. 1: 2

Correct answer: 4: 1

Solution

Since I = n*A*e*v_d is the same and A is equal, v_d is inversely proportional to n; with n1:n2 = 1:4, v_d ratio = 4:1.

Related JEE Main Physics questions

• A physical quantity X is defined as ε0L(ΔV/Δt), where ε0 denotes the permittivity of free space, L is a length, ΔV is a potential difference, and Δt is a time interval. The dimensional formula of X matches that of which of the following?
• A set of n identical resistors is arranged once in a series combination and once in a parallel combination. What is the ratio of the larger equivalent resistance to the smaller equivalent resistance?
• A resistance coil is connected to a battery. In which arrangement will the maximum heat be produced?
• A bulb is rated at 220 V and 100 W. If the applied voltage falls by 2.5% from its rated value, by what percentage of the rated power will the power output decrease?
• An ammeter has a coil resistance of R. To extend its measuring range by a factor of n, the shunt resistance needed should be:
• How does the drift velocity Vd depend on the strength of the applied electric field?

⚔️ Practice JEE Main Physics free + battle 1v1 →