Question

A 40 mu F and a 6.0 mu F capacitor are connected in series across an 8.0 V DC source. What is the charge on the 4.0 mu F capacitor? A) 19 mu C B) 25 mu C C) 4.0 mu C D) 2.0 mu C E) 12 mu C A system of capacitors is across a 90 V DC voltage source as shown in Fig, 16-6. What is the equivalent capacitance of this system? A) 15 mu F B) 1.5 mu F C) 3.6 mu F D) 3.3 mu F E) None of the other answers is correct. An electron moving perpendicular to a magnetic field of 2.2 times 10^-2 T moves in a circle of certain radius. If the electron is moving with a speed of 1.5 times 10^7 m/s, what is the radius of the circle? A) 39 times 10^-4 m B) 1.5 times 10^-3 m C) 2.2 times 10^-3 m D) 2.2 times 10^-4 m E) 3.9 times 10^-3 m Rayleigh scattering would have 400. nm light be scattered how many times as much as 800.nm light? A) 4 B) 2 C) 8 D) 32 E) 16 Two coins carry identical charges. These two coins are lying 2.00 m apart on a table. If each of these coins experiences a force of 2.00 N, how large is the charge on each coin? A) 29.8 mu C B) 6.67 mu C C) 1.49 mu C D) 14.9 mu C E) 2.98 mu C

Answer 1

here,

C1 = 4 uF = 4 * 10^-6 F

C2 = 6 * 10^-6 F

the equivalent capacitance , C = C1 * C2 /( C1 + C2)

C = 4 * 10^-6 * 6 * 10^-6 /( 4 * 10^-6 + 6 * 10^-6)

C = 2.4 * 10^-6 F

V = 8 V

the charge across 4 uF , Q = C * V

Q = 2.4 * 10^-6 * 8 C

Q = 19 * 10^-6 C

Q = 19 uC

the charge is A) 19 uC