• Check answers – a few were found to be wrong…possibly reword the definition/law questions

Electrostatics JEOPARDY

Powell

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WilliamsBrownHeadAugustine

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A

Balloons X , Y  and Z  are  hanging as shown.   Balloon X  is positively-charged

Balloon Y  ____. 

                                                  

A must be positively-charged

D could be either negatively-charged or neutral

B must be negatively-charged

E could be either positively-charged or neutral

C must be neutral

 

What is

D. could be either negatively-charged

or neutral?

The charge an electrophorus would gain if the base was made

out of glass.

A

What is

Negative?

The reason that scraps of paper jump up and down and back

up when a charged plastic rod is brought near.

A

What is

The pieces become polarized, are attracted to the rod, and jump up.

When they touch, the charge is transferred to the piece, giving it the same charge. The attraction

stops. When it touches ground, it looses its charge, allowing it to

become polarized again ?

Explanation of the basic process of charging an electroscope.

A

What is

A charged object is touched to the ball of the electroscope. The

charges are transferred andtravel across the bars of the scope, causing it to repel ?

Explanation of how one’s hair raises when you touch the Van

de Graaff generator.

A

What is

Negative charges travel from the Van de Graaff generator onto

one’s body as they try to get asthey try to spread out. When on your hair, they cause it to raise up as they try to repel as far as possible ?

The magnitude of the force of a +25µC charge on a -50µC

charge 20 cm away.

A

+25µC -50µC

22cm

9x109 (50 x 10-6 C) (25 x 10-6 C) Nm2 C2

(.20 m)2

What is

2.81 x 102 N ?

= 2.81 x 102 N

F =k Q1Q2

r2

The magnitude of the force 10 electrons would apply on 4

protons at a distance of 1µm.

AHint…qe=1.6x10-19 C

What is

9.22 x 10-15 N ?

9x109 [10(1.6 x 10-19 C)] Nm2 C2

(1 x 10-6 m)2

[4(1.6 x 10-19 C)] = 9.22 x 10-15 N

F =k Q1Q2

r2

The force applied on the farthest right charge by the other two

charges.

A

+8µC -6µC

7mm 3mm

+5µC

9x109 (8 x 10-6 C) (5 x 10-6 C) Nm2 C2

(10 x 10-3 m)2

= 3.6 x 103 N

What is

2.64 x 104 N left ?

9x109 (6 x 10-6 C) (5 x 10-6 C) Nm2 C2

(3 x 10-3 m)2

= 3 x 104 N

F13 =

F23 =

F23 + F13 = 2.64 x 104 left

F =k Q1Q2

r2

The number of electrons you would need to put on

electrostatic flying boots to make a 70kg person hover at a height of 2 m above a charge of

-50 mC.

A

Ahhh..

I’m flying!

What is

2.38 x 1012?

F = 70kg (9.81 m/s2) = 9x109 (-50 x 10-3 C) [n(-1.6 x 10-19 C)]

Nm2 C2

(.20 m)2

n = 2.38 x 1012

F =k Q1Q2

r2

The force on the orange charge.

A

+4.6 C

-5.4 C +4.6 C

-5.4 C

5 m

4 m

2.5 m

2 m

+ 7.2 C

What is

0 N ?

Diagonal forces cancel each other out, resulting in a net force of 0N on the orange charge.

F =k Q1Q2

r2

No net electric charge can be created or destroyed.

A

What is

The law of conservation of electric charge ?

+1.6 x 10-19 C

A

What is

The Charge of a proton ?

The charging of an isolated conducting object by grounding

it while a charged body is nearby.

A

What is

Induction ?

The force F exerted on a tiny positive test charge placed

divided by the magnitude of the test charge.

A

What is

Electric Field, E ?

E = F

q

Two equally charged charge that have the opposite charge.

A

What is

A dipole ?

A

The charge of the orange charge

Followed by

The charge of the blue charge

What is

Positive (orange), negative (blue) ?

A

|Q|=4.7 x 10-4 C

Charge on the blue charge

What is

-3.5 x 10-4 C ?

4.7 x 10-4 C

?=

8 lines

6 lines

|Q|=4.7 x 10-4 C

A

The number of lines that should point outwards from

the orange plate.

BE CAREFUL!!!!

?

?

What is

0 ?

Follow up question

How many lines should point inwards?

8 lines8 charges =

?6 charges

A

Charges of point charges in order (orange, blue, green, white)

What is

- - + + ?

Orange

Blue

Green

White

Minimum of 2 errors in the following drawing, with

explanations of error.

A

2 C2 C

What are

Wrong direction of field lines (should go from positive to

negative) and

Wrong number of field lines (should be equal as charge is

equal) ?

E-Field at X below

A

12 C

15m

What is

6 x 108 N/C left ?

12 C

15m

9x109 (12 C) Nm2 C2

(15 m)2

= 6 x 108 N/C

E =k Q

r2

A

Approximate location of E=0 N/C on line between orange and blue

charge

12 C

15m

24 C

What is

Somewhere between orange and mid point (7.5m to the right of

orange) ?

12 C

15m

24 C

E =k Q

r2

The E-Field at the X

A

12 C

15m

24 C

10 m

What is

2.33 x 109 N/C right ?

E =k Q

r2

12 C

15m

24 C

10 m

E24CE12C

9x109 (12 C) Nm2 C2

(25 m)2

= 1.7 x 108 N/C

9x109 (24 C) Nm2 C2

(10 m)2

= 2.16 x 109 N/C

The letter which denotes the location with the greatest

magnitude of E-Field

A

AB C D

1m4m 3m 2m

Q=1.5C Q=24C Q=18C Q=7C

What is

C ?

E =k Q

r2

EA =k (1.5C)

(1m)2=1.5k C/m2

EB =k (24C)

(4m)2=1.5k C/m2

EC =k (18C)

(3m)2=2k C/m2

ED =k (7C)

(2m)2=1.75k C/m2

A

The E-Field at the orange point.

-4 C

-5 C +4 C

-5 C

5 m

5 m

2.5 m

2.5 m

2.5m

2.5m3.53m=r

E =k Q

r2

9x109 (4 C) Nm2 C2

(3.53 m)2

= 2.89 x 109 N

What is

5.77 x 109 N 45 degrees N of W ?

FINAL JEOPARDY

The complete process for charging an electrophorus using proper terminology.

(5 minutes)

TIE BREAKER

WHAT IS THE SIGNIFICANCE OF THE CATEGORY TITLES?

2004 Illini Basketball Starters(when we should have won the

NCAA tourney)