Blog Archive

Monday, July 9, 2012

Q.407. Electrostatic potential

Question 407.
A small object with a mass of 270 mg carries a charge of 35.0 nC and is suspended by a thread between the vertical plates of a parallel-plate capacitor. The plates are separated by 2.00 cm. If the thread makes an angle of 14.0° with the vertical, what is the potential difference between the plates?

Answer 407.
Let T = tension in the thread
and F = electrostatic force on the charge
For static equilibrium, balancing forces in the horizontal and vertical directions,
mg = Tcos14° and
F = Tsin14°
Taking the ratio,
F = mgtan14° ... ( 1 )

If V = potential difference between the plates,
electric field between the plates
= V/d = V/0.02 N/C
=> force on the charge
F = 35.0 x 10^-9 V/(0.02) ... ( 2 )
 From ( 1 ) and ( 2 ),
35.0 x 10^-9 V/(0.02) = mgtan14°
=> Potential difference between the plates, V
= (0.02mgtan14°) / (35.0 x 10^-9)
= (0.02 * 270 x 10^-6 * 9.81 * tan14°) / (35.0 x 10^-9) volt
= 377.4 volt.

Link to YA!

2 comments:

  1. Please is there a way that i can post questions and get them solved? My exams are approaching and im finding some questions really difficult. I would be most greatful. Thanks

    ReplyDelete
  2. You can post your questions on answers.yahoo.com which is a free website of Yahoo where there are thousands of subject experts ready to answer your questions. After posting the question, if you send me the link of your question, I shall answer it if I can.

    ReplyDelete