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The SI units of the current density is ________.

Asked in GUJCET 2024 · Drift velocity, mobility and current density

• (1) Am⁻¹
• (2) Am²
• (3) Am⁻³
• (4) Am⁻²

Step-by-step solution

Why the other options are wrong

• (1) Ampere per metre is current per unit length; it is the unit of the magnetising field H. Current density divides the current by an area.
• (2) Am² multiplies the current by an area instead of dividing by it. Current times area is the unit of a magnetic dipole moment.
• (3) Ampere per cubic metre is current per unit volume. In J = I/A the divisor is the area of cross-section, not a volume.

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