Electric Field Intensity Measurement

Description:

We know that,

E→ = F→/q .........(1)

Here,  electric field intensity (E) is a vector quantity and its direction is same as that of force experienced by the test charge.

F→ = qE→ ........(2)

When a source charge (Q) applies force on a test charge(q), then the force experienced by the test charge is given by −

F→_PQ = 1/4πε₀qQ/r²r̂_qQ .......(3)

from 1 and 3;

qE→ = 1/4πε₀qQ/r²r̂_qQ

E→ = 1/4πε₀qQ/r²qr̂_qQ

E→ = 1/4πε₀Q/r²r̂_qQ

Note −

Electric field intensity (E) when test charge is given: E→ = F→/q

Electric field intensity (E) when source charge is given: E→ = 1/4πε₀Q/r²r̂_qQ

• Unit of E −

  Since E→ = F→/q

  Therefore, unit is: E = NC^-1

• Dimension of E −

  |E| = MLT^-2/AT

  |E|→ = MLT^-3A^-1

Note −

1. Electric field intensity (E) is having a sign also.

• If the source charge (Q) is negative (-) then electric field intensity (E) will also be (-).
• If the source charge (Q) is positive (+) then the electric field intensity (E) will also be (+).

2. The test charge (q) is always considered as  positive (+)

3. If force on ‘q’ is directed towards the source charge (Q) (i.e q is experiencing force of attraction) it means Q is (-ve).

4. If ‘q’ is directed away from the source charge (Q) (i.e q is experiencing force of repulsion) it means Q is (+ve ).