Question 1

A $$+5.0\ \mu\mathrm{C}$$ charge is placed at the origin of a coordinate system. A $$-10.0\ \mu\mathrm{C}$$ charge is placed at $$+50\ \mathrm{cm} on $$the x-axis. Where is the total electric field zero?

Accepted Answer

$$-121\ \mathrm{cm}$$

Question 2

A $$2.0\ \mathrm{F}$$ capacitor is connected to a $$10.0\ \mathrm{V}$$ battery and acquires a charge $$Q$$ and some potential energy $$PE_1. $$The battery is then disconnected and the charged capacitor is connected to a second uncharged capacitor of size $$4.0\ \mathrm{F}. $$What is the change in the total potential energy, $$PE_2$$ - $$PE_1$$?

Accepted Answer

$$-33.3\ \mathrm{J}$$

Question 3

Two charges, $$+5.0\ \mu\mathrm{C}$$ and $$-10.0\ \mu\mathrm{C}$$, are $$10\ \mathrm{cm}$$ apart. What is the potential energy of this pair of charges?

Accepted Answer

$$-4.5\ \mathrm{J}$$

Question 4

A resistor carries $$3.4\ \mathrm{A}$$ and dissipates $$56.7\ \mathrm{W}. $$What is the size of the resistance?

Accepted Answer

$$4.9\ \Omega$$

Question 5

In the circuit shown, what is the size of the current in the $$20\ \Omega$$ resistor if the batteries are $$20\ \mathrm{V}$$ and $$10\ \mathrm{V} as $$shown?

Accepted Answer

$$0.64\ \mathrm{A}$$

Question 6

Two identical tiny spheres each have mass $$m$$ and carry a charge of $$2.5\ \mu\mathrm{C}. $$They hang from the ceiling from very thin threads that are $$50\ \mathrm{cm}$$ long. The angle from either thread to a vertical line is $$35^\circ. $$What is the value of the mass $$m$$?

Accepted Answer

$$0.0249\ \mathrm{kg}$$

Question 7

A $$150\ \mathrm{g}$$ ball is tossed straight upward. It carries a charge of $$+5.0\ \mathrm{mC}. It is $$launched at $$30\ \mathrm{m/s}$$ and after it moves upward by $$10\ \mathrm{m} it is $$moving at $$15\ \mathrm{m/s}. If it is $$moving in a uniform electric field that is directed either up or down, what is the size and direction of the electric field?

Accepted Answer

$$78.5\ \mathrm{N/C}$$, downward

Question 8

A charging RC circuit has a current of $$0.50\ \mathrm{A} at $$some time $$T$$ after the charging process begins. Given $$\Delta V_0$ = 25\ \mathrm{V}$$, $$R = 10\ \Omega$$, $$C = 0.25\ \mathrm{F}$$, find the time $$T.$$

Accepted Answer

$$0.402\ \mathrm{s}$$

Question 9

Which of the following best describes the energy lost when two capacitors are connected together after one is charged and the other is uncharged?

Accepted Answer

The energy is lost as heat due to the redistribution of charge.

Question 10

If the distance between two point charges is doubled, what happens to the electric force between them?

Accepted Answer

It becomes one-fourth as large.

Question 11

A $$10\ \Omega$$ resistor is connected in series with a $$0.25\ \mathrm{F}$$ capacitor and a $$25\ \mathrm{V}$$ battery. What is the time constant $$	au of $$the circuit?

Accepted Answer

$$2.5\ \mathrm{s}$$

Question 12

A $$2.0\ \mathrm{F}$$ capacitor is charged to $$10.0\ \mathrm{V}. $$What is the energy stored in the capacitor?

Accepted Answer

$$100\ \mathrm{J}$$

Question 13

Which of the following statements about electric potential energy is correct?

Accepted Answer

It can be negative if the charges are of opposite sign.

Question 14

A $$3.4\ \mathrm{A}$$ current flows through a resistor. If the resistance is doubled, what happens to the power dissipated?

Accepted Answer

It is halved.

Question 15

A $$5.0\ \mu\mathrm{C}$$ charge is brought from infinity to a point $$10\ \mathrm{cm}$$ from a $$-10.0\ \mu\mathrm{C}$$ charge. What is the change in potential energy?

Accepted Answer

$$-4.5\ \mathrm{J}$$

Physics 207 Exam #1 Study Guidance: Electric Fields, Capacitors, Potential Energy, and Circuits

Study Guide - Practice Questions

Study Guide - Flashcards