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A small plastic ball with a mass of 7.00 10-3 kg and with a charge of +0.155 µC is suspended from an insulating thread and hangs between the plates of a capacitor (see the drawing). The ball is in equilibrium, with the thread making an angle of 30.0° with respect to the vertical. The area of each plate is 0.0135 m2. What is the magnitude of the charge on each plate?

Respuesta :

Answer:

the magnitude of the charge Q on each plate is [tex]3.053 *10^{-8} \ C[/tex]

Explanation:

Given that :

mass (m) = [tex]7.00 *10 ^{-3} \ kg[/tex]

charge (q) = +0.155 µC = [tex]+0.155 *10^{-6}\ C[/tex]

angle [tex]\theta = 30^0 \ C[/tex]

Area A on each plate = 0.0135 m²

From the diagram below;

[tex]tan \ \theta = \frac{Eq}{mg}[/tex]    ----- equation (1)

Also by using Gauss Law ;

[tex]Q = \epsilon_0 \phi[/tex]

[tex]Q = \epsilon_0EA[/tex]     ----- equation (2)

Combination equation 1 and 2 together ; we have

[tex]Q = \frac{\epsilon_0\ * \ m\ *\ g \ \ * \ tan \theta \ * \ A}{q}[/tex]

[tex]Q = \frac{(8.85*10^{-12}C^2/N.m^2 )\ * \ (7.00*10^{-3} kg)\ *\ (9.8 m/s^2) \ \ * \ tan \(30 \ * \ (0.0135 m^2)}{0.155*10^{-6}\ C}[/tex]

[tex]Q = 3.053 *10^{-8} \ C[/tex]

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