Question

If L >> r and the charge per unit length on the rod is l then the angle the thread makes with the line charge is-

• A. $\tan^{- 1}\left( \frac{q\lambda}{2\pi\varepsilon_{0}rmg} \right)$
• B. tan^–1$\left( \frac{q}{2\pi\varepsilon_{0}mg} \right)$
• C. tan^–1$\left( \frac{q}{2\pi\varepsilon_{0}\lambda mg} \right)$
• D. tan^–1$\left( \frac{\lambda}{2\pi\varepsilon_{0}qmg} \right)$

Answer 1

Answer: (A)

$\tan^{- 1}\left( \frac{q\lambda}{2\pi\varepsilon_{0}rmg} \right)$

Answer 2

T cos q = mg & T sin q = qE

tan q = $\frac { \mathrm { qE } } { \mathrm { mg } }$ Ž q = tan^–1 $\left( \frac { \mathrm { q } \lambda } { \mathrm { mg } 2 \pi \varepsilon _ { 0 } \mathrm { r } } \right)$