Question

The field around direct current carrying conductor is/are (where E and B are respectively represent electric field and magnetic field)
1. Only E
2. Neither E nor B
3. Only B
4. both E and B

Answer 1

Correct Answer - Option 3 : Only B

Concept: 

• Magnetic field due to a straight current-carrying conductor: Biot-Savart Law
  • ​Magnetic field B at a radial distance r, due to a wire carrying current is given by:

\(B = \frac{μ_0I}{2π r}\)

Where μ0 is the permeability of free space (4π × 10-7 Tm/A), and I is the current intensity.

Explanation:

• So a current-carrying wire has a magnetic field around it. 
• Electromagnets are based on this principle. 
• The wire does not have an electric field around it. 
• A single charge stationary has an electric field around it. 
• But, when the charge is moving in a conductor, the net electric charge across the wire will be zero, as the number of electrons entering the conductor is equal to charges exit from the conductor. 
• Also according to the gauss law, if the charge enclosed is zero, the net field will be zero. 

So there is only a magnetic field.