Question

An electric dipole consists of two equal and opposite charges placed `2 cm` apart. When the dipole is placed in a uniform electric field of strength `10^(5)NC^(-1)`, it experiences a maximum torque of `0.2xx10^(-3)Nm`. Find the magnitude of each charge
A. `20 mu m`
B. `10 muC`
C. `15 muC`
D. `40 muC`

Answer 1

Correct Answer - b
Hence, `2a= 2cm= 0.02m, tau_(max)= 0.2xx10^(-3)Nm` and `E=10^(5)NC^(-1)`
Now, maximum torque on the dipole,
`tau_(max)= pE= q(2a)xxE`
`:. Q=(ta_(max))/((2a)E)=(0.2xx10^(-3))/(0.02xx10^(5))= 10^(-7)C= 10 mu C`