COMEDK · Physics · 17. Electrostatics
A tiny ball of mass \(\mathrm{m}\) and charge \(\mathrm{q}\) is suspended from the fixed support using an insulating string of length \(1 \mathrm{~m}\). The horizontal uniform electric field \(\mathrm{E}\) is switched on. The angle made by the string with vertical when the ball is in equilibrium is \(45^{\circ}\). The magnitude of uniform electric field is
- A \(E=\dfrac{m g}{\sqrt{2} q} \quad N C^{-1}\)
- B \(E=\dfrac{m g}{q} \quad N C^{-1}\)
- C \(\mathrm{E}=0 \quad \mathrm{NC}^{-1}\)
- D \(\mathrm{E}=\dfrac{\sqrt{2} \mathrm{mg}}{\mathrm{q}} \mathrm{NC}^{-1}\)
Answer & Solution
Correct Answer
(B) \(E=\dfrac{m g}{q} \quad N C^{-1}\)
Step-by-step Solution
Detailed explanation
Let the mass of the ball be \(m\), charge be \(q\), and the electric field be \(E\). The forces acting on the ball in equilibrium are: 1. Gravitational force \(mg\) acting vertically downwards. 2. Electric force \(qE\) acting horizontally. 3. Tension \(T\) in the string acting…
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