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Class 12 › Physics › Electric Charge and Field
CBSE2024Class Class 12 · Physics2 Marks · Short✅ Verified
If the electric field is given by E = 6î + 3ĵ + 4k̂, calculate the electric flux through a surface of area 20 units lying in the yz-plane.
✅ Answer & Solution
<b>Given:</b><br>• Electric field: E = 6î + 3ĵ + 4k̂<br>• Surface area = 20 units<br>• Surface lies in the <b>yz-plane</b><br><br><b>Step 1: Identify the area vector</b><br>Since the surface lies in the yz-plane, its <b>normal is along the x-axis</b>.<br><br><b>Area vector:</b> A = 20 î<br><br><b>Step 2: Apply formula for electric flux</b><br>φ = E · A (dot product)<br><br><b>Step 3: Calculate dot product</b><br>φ = (6î + 3ĵ + 4k̂) · (20 î)<br><br>φ = (6 × 20) + (3 × 0) + (4 × 0)<br><br>φ = 120 + 0 + 0<br><br><b>φ = 120 units</b><br><br><b>Final Answer:</b><br>Electric flux through the surface = <b>120 N·m²/C</b> (or 120 in given units)<br><br><b>Note:</b> Only the x-component of E contributes to the flux, since the area vector is along x-axis.