Step 1: Understanding current density.
Current density is defined as the amount of current flowing per unit area. It is given by the formula:
where is the current density, is the current, and is the cross-sectional area. The unit of current density is thus amperes per square meter (A/m²).
Step 2: Explanation of each option.
- (A) ampere (A): Incorrect. Ampere is the unit of current, not current density.
- (B) coulomb (C): Incorrect. Coulomb is the unit of charge, not current density.
- (C) ampere per square metre (A/m²): Correct. This is the correct unit for current density.
- (D) volt per metre (V/m): Incorrect. This is the unit of electric field, not current density.
Step 3: Conclusion.
The unit of current density is amperes per square meter (A/m²).