Question

a 0.200g ball hangs from a thread in a vertical electric field of 3.00kN/C directed upward. what is the charge on the ball if the tension in the thread is (a) zero and (b) 4.00mN?

Answer 1

Given:

A 0.200g ball hangs from a thread in a vertical electric field of 3.00kN/C directed upward.

To find:

Charge on ball when

• tension is zero and 4 mN ?

Calculation:

When tension is zero, we can say:

$\sf mg = Eq$

$\sf \implies \dfrac{0.2}{1000} \times 10 = 3000 \times q$

$\sf \implies \dfrac{0.2}{100} = 3000 \times q$

$\sf \implies q = \dfrac{0.2}{100 \times 3000}$

$\sf \implies q = \dfrac{2}{1000 \times 3000}$

$\sf \implies q = 0.67 \times {10}^{ - 6}$

$\sf \implies q = 0.67 \: \mu C$

So, charge is 0.67 micro-C.

Now, when tension is 4 mN:

$\sf mg = Eq + T$

$\sf \implies \dfrac{0.2}{1000} \times 10 =( 3000 \times q) + 4 \times {10}^{ - 3}$

$\sf \implies 0.002 =( 3000 \times q) + 0.004$

$\sf \implies - 0.002 =( 3000 \times q)$

$\sf \implies q = - 0.67 \: \mu C$

Hope It Helps.