# Unit 7 Concepts Quiz

10 Questions | Total Attempts: 180  Settings  • 1.
Two charged balls are repelling each other as they hang from the ceiling.   What can you say about their charges?
• A.

One is positive, the other is negative

• B.

Both are positive

• C.

Both are negative

• D.

Both are positive or both are negative

• 2.
A metal ball hangs from the ceiling by an insulating thread.  The ball is attracted to a positive-charged rod held near the ball.  The charge of the ball must be:
• A.

Positive

• B.

Negative

• C.

Neutral

• D.

Positive or neutral

• E.

Negative or neutral

• 3.
The force between two charges separated by a distance d is F.  If the charges are pulled apart to a distance 3d, what is the force on each charge?
• A.

9F

• B.

3F

• C.

F

• D.

1/3F

• E.

1/9F

• 4.
A proton and an electron are held apart a distance of 1 m and then released.   As they approach each other, what happens to the force between them?
• A.

It gets bigger

• B.

It gets smaller

• C.

It stays the same

• 5.
You are sitting a certain distance from a point charge, and you measure an electric field of E0.   If the charge is doubled and your distance from the charge is also doubled, what is the electric field strength now?
• A.

4E

• B.

2E

• C.

E

• D.

1/2E

• E.

1/4E

• 6.
A proton and an electron are in a constant electric field created by oppositely charged plates.  You release the proton from the positive side and the electron from the negative side.  Which feels the larger electric force?
• A.

Proton

• B.

Electron

• C.

Both feel the same force

• D.

Neither – there is no force

• E.

They feel the same magnitude force but opposite direction

• 7.
Capacitor C1 is connected across a battery of 5 V.  An identical capacitor C2 is connected across a battery of 10 V.  Which one has the most charge?
• A.

C1

• B.

C2

• C.

Both have the same charge

• D.

It depends on other factors

• 8.
What must be done to a capacitor in order to increase the amount of charge it can hold (for a constant voltage)?
• A.

Increase the area of the plates

• B.

Decrease separation between the plates

• C.

Decrease the area of the plates

• D.

Either (1) or (2)

• E.

Either (2) or (3)

• 9.
A parallel-plate capacitor initially has a potential difference of 400 V and is then disconnected from the charging battery.  If the plate spacing is now doubled (without changing Q), what is the new value of the voltage?
• A.

100 V

• B.

200 V

• C.

400 V

• D.

800 V

• E.

1600 V

• 10.
Consider point charges of +Q and +4Q, which are separated by 3.0 m.  At what point, on a line between the two charges, would it be possible to place a charge of -Q such that the electrostatic force acting on it would be zero?
• A.

There is no such point possible.

• B.

1.0 m from the +Q charge

• C.

1.0 m from the +4Q charge

• D.

0.60 m from the +Q charge

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