Question

1.) What are the sign and magnitude in coulombs of a point charge that produces a potential of -2.50 V at a distance of 2.00mm?

C

2.)

a) What is the capacitance (in µF) of a parallel plate capacitor having plates of area 1.25 m² that are separated by 0.0210 mm of strontium titanate?

µF

(b) What charge (in µC) does it hold when 9.00 V is applied to it?

µC

Answer 1

1)

we know that the potential of a point charge q at a point p at a distance r is  

v(r) = k*q/r

given v = -2.50 V , r = 2.0 mm = 0.002 m

-2.50= 9*10^9*q/0.002

q = -5.556*10^-13 C

q = -0.5556 *10^-12 C  

the charge is -ve charge and magnitude is -0.556*10^-12 C

2.

Area A = 1.25 m^2 , separation of plates d = 0.0210 mm

we know that the capacitance of a parallel plate capacitor is  

C = epsilon not*A/d

C = 8.854*10^-12*1.25/(0.0210*10^-3) F

C = 5.2702380952381*10^-7 F

C = 0.5270*10^-6 F

C = 0.5270 µF

3.

from the relation between charge , Capacitance and voltage is  

Q = C*V

Q = 0.5270*10^-6*9 C

Q = 4.743*10^-6 C

the charge is Q = 4.743*10^-6 C