Physics 314 Unit 10 Warmups: 2015-2016

Warmup: Thur Jan. 21What is the total charge in

Coulombs for a sample of 25 sulfate ions?

(SO4 has a charge of -2)

Warmup: Thur Jan. 21What is the total charge in Coulombs for a sample of 25 sulfate

ions (SO4 has a charge of -2)

Q = NeQ = (25)(-2)(1.6 x 10-19 C)

-8.0 x 10-18 C

Warmup: Friday, January 22:

•What is the number of electrons required to create a net charge of -45 nC?

What is the number of electrons required to create a net charge of -45 nC?

q = Neq/e = Nq = 45 nC = 4.5 x 101 nC = 4.5 x 10-8 C

4.5 x 10-8 C / 1.6 x 10-19 C = N2.81 x 1011 electrons required!

Monday, February 1st

Warmup: Draw Electric Field Lines for the following:

Checklist:

• No Lines crossed• Diamond between

two +3 charges•Watermelon

between each +3 and the -2• 3:3:2 ratio between

lines• Arrows away from

+, toward – charges and towards - charge

+3

-2+3

Tuesday, February 2nd

What is the net force on the middle charge?

d12 = 12 cm d23 = 3 cm

Q1 3 μC

Q2

4 μCQ3

2μC

Tuesday, February 2nd

What is the net force on the middle charge?

d12 = 12 cm d23 = 3 cm

F32 F12

Q1 3 μC

Q2

4 μCQ3

2μC

Wednesday, Feb. 3rd: What is the magnitude and direction of the electric field acting upon the charge shown below if it feels a force of 8.0 x 10-6 N?:

FE-4.0 μC

What is the magnitude and direction of the electric field acting upon the charge shown below if it feels a force of 8.0 x 10-6 N?:

FE-4.0 μC

Direction: for negative charges, electric field is in reverse direction as electric force, so electric field is to the LEFT.Magnitude:E = FE/q2

= (8.0 x 10-6 N / 4.0 x 10-6 C= 2.0 N/C

What is the electric field at the top of the ball as a result of the orange charge (-6 μC)? The orange charge is in the exact middle of the 80 cm ball.

What is the electric field at the top of the ball as a result of the orange charge (-6 μC)? The orange charge is in the exact middle of the 80 cm ball.

Magnitude: E = kq1/r2

E = (9 x 109 Nm2/C2) (-6 x 10-6C) / (0.40 m)2

E = 3.38 x 105 N/C

Direction: Electric field lines go inward toward negative charges. Therefore, E field lines will go DOWNWARD through the top of the ball to get to the charge