PHY 192 Exam 3 – Flashcards

If the electric field is zero everywhere inside a region of space, the potential must also be zero in that region. (T/F)

When the electric field is zero at a point, the potential must also be zero there. (T/F)

If the electrical potential in a region is constant, the electric field must be zero everywhere in that region. (T/F)

If the electric potential at a point in space is zero, then the electric field at that point must also be zero. (T/F)

A negative charge, if free, will tend to move:

Suppose a region of space has a uniform electric field, directed towards the right, as shown in the figure. Which statement about the electric potential is true?

Which statements are true for an electron moving in the direction of an electric field?

Suppose you have two point charges of opposite sign. As you move them farther and farther apart, the potential energy of this system relative to infinity:

Suppose you have two negative point charges. As you move them farther and farther apart, the potential energy of this system relative to infinity:

Two equal positive charges are held in place at a fixed distance. If you put a third positive charge midway between these two charges, its electrical potential energy of the system (relative to infinity) is zero because the electrical forces on the third charge due to the two fixed charges just balance each other. (T/F)

A negative charge is moved from point A to point B along an equipotential surface. Which of the following statements must be true for this case?

A conducting sphere of radius R carries an excess positive charge and is very far away from any other charges. Which one of the following graphs best illustrates the potential (relative to infinity) produced by this sphere as a function of distance r from the center of the sphere?

A metallic sphere of radius 5cm is charged such that the potential of its surface is 100V. Which of the following plots correctly shows the potential as a function of distance from the center of the sphere?

A nonconducting sphere contains positive charge distributed uniformly throughout its volume. Which statements about the potential due to this sphere are true?

A conducting sphere contains positive charge distributed uniformly over its surface. Which of the statements about the potential due to this sphere are true?

The graph in the figure shows the variation of the electric potential V as a function of the radial direction r. For what range or value of r is the magnitude of the electric field the largest?

The graph in the figure shows the variation of the electric potential V(x) as a function of the position x. Which of the choices below correctly describes the orientation of the x-component of the electric field along the x-axis?

The potential as a function of position x is shown in the graph in the figure. Which statement about the electric field is true?

The charge on the square plates of a parallel-plate capacitor is Q. The potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. The amount of charge on the plates is now equal to:

The electric field between the square plates of a parallel-plate capacitor has a magnitude E. The potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared tot he dimensions of the plates. The magnitude of the electric field between the plates is now equal to:

Equal but opposite charges Q are placed on square plates of an air-filled parallel-plate capacitor. The plates are then pulled apart to twice their original separation, which is small compared to the dimensions of the plates. Which of the following statements about this capacitor are true?

When two or more capacitors are connected in series across a potential difference:

When two or more capacitors are connected in parallel across a potential difference:

The four identical capacitors in the circuit shown in the figure are initially uncharged. Let the charges on the capacitors be Q1, Q2,Q3, and Q4 and the potential differences across them be V1,V2,V3, and V4. The switch is thrown first to position A and kept there for a long time. It is then thrown to position B. Which of the following conditions is true with the switch in position B?

In the circuit shown in the figure, the capacitors are initially uncharged. The switch is first thrown to position A and kept there for a long time. It is then thrown to position B. Let the charges on the capacitors be Q1,Q2, and Q3 and the potential differences across them be V1,V2, and V3. Which of the following conditions must be true with the switch in position B?

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a very small distance d. When this capacitor is connected to a battery that maintains a constant potential difference between the plates, the energy stored in the capacitor is Uo. If the separation between the plates is doubled, how much energy is stored in the capacitor?

An ideal parallel-plate capacitor consists of a set of two parallel plates of area A separated by a very small distance d. When the capacitor plates carry charges +Q and -Q, the capacitor stores energy Uo. If the separation between the plates is doubled, how much electrical energy is stored in the capacitor?

An ideal air-filled parallel-plate capacitor has round plates and carries a fixed amount of equal but opposite charge on its plates. All the geometric parameters of the capacitor (plate diameter and plate separation) are now DOUBLED. If the original capacitance was Co, what is the new capacitance?

An ideal air-filled parallel-plate capacitor has round plates and carries a fixed amount of equal but opposite charge on its plates. All the geometric parameters of the capacitor (plate diameter and plate separation) are now DOUBLED. If the original energy stored in the capacitor was Uo, how much energy does it store now?

An ideal air-filled parallel-plate capacitor has round plates and carries a fixed amount of equal but opposite charge on its plates. All the geometric parameters of the capacitor (plate diameter and plate separation) are now DOUBLED. If the original energy density between the plates was uo, what is the new energy density?

A charged capacitor stores energy U. Without connecting this capacitor to anything, dielectric having dielectric constant K is now inserted between the plates of the capacitor, completely filling the space between them. How much energy does the capacitor now store?

Two capacitors, C1 and C2, are connected in series across a source of potential difference. With the potential source still connected, a dielectric is now inserted between the plates of capacitor C1. What happens to the charge on capacitor C2?

An air-filled parallel-plate capacitor is connected to a battery and allowed to charge up. Now a slab of dielectric material is placed between the plates of the capacitor while the capacitor is still connected to the battery. After this is done, we find that:

The figure shows a stead electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

When electric current is flowing in a metal, the electrons are moving:

The figure shows two connected wires that are made of the same material. The current entering the wire on the left is 2.0A and in that wire the electron drift speed is vd. What is the electron drift speed in the wire on the right side?

A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b, forming one long wire of length 2L. This long wire is attached to a battery, and a current is flowing through it. If the electric field in the narrow wire is E, the electric field in the wide wire is:

A cylindrical wire has a resistance R and resistivity p. If its length and diameter are BOTH cut in half, a. What will be its resistance? b. What will be its resistivity?

You are given a copper bar of dimensions 3cmx5cmx8cm and asked to attach leads to it in order to make it a resistor. a. If you want to achieve the SMALLEST possible resistance, you should attach the leads to the opposite faces that measure: b. If you want to achieve the LARGEST possible resistance, you should attach the leads to the opposite faces that measure:

A wire of resistivity p must be replaced in a circuit by a wire of the same material but 4 times as long. if, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be:

As current flows through a uniform wire, the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire. (T/F)

When a potential difference of 10V is placed across a certain solid cylindrical resistor, the current through it is 2A. If the diameter of this resistor is now tripled, the current will be:

Two cables of the same length are made of the same material, except that one cable has twice the diameter of the other cable. When the same potential difference is maintained across both cables, which of the following statements are true?

As more resistors are added in parallel across a constant voltage source, the power supplied by the source:

The figure shows three identical lightbulbs connected to a battery having a constant voltage across its terminals. What happens to the brightness of lightbulb 1 when the switch S is closed?

In the circuit shown in the figure, all the lightbulbs are identical. Which of the following is the correct ranking of the brightness of the bulbs?

In the circuit shown in the figure, four identical resistors labeled A to D are connected to a battery as shown. S1 and S2 are switches. Which of the following actions would result in the GREATEST amount of current through resistor A?

A resistor is made out of a long wire having length L. Each end of the wire is attached to a terminal of a battery providing a constant voltage, Vo. A current I flows through the wire. If the wire were cut in half, making two wires of length L/2, and both wires were attached to the battery (the end of both wires attached to one terminal, and the other ends attached to the other terminal), what would be the total current flowing through the two wires?

A light bulb is connected in the circuit shown in the figure with the switch S open. All the connecting leads have no appreciable resistance and the battery has no internal resistance. When we close the switch, which statements below accurately describe the behavior of the circuit?

Two lightbulbs, B1 and B2, are connected to a battery having appreciable internal resistance as shown in the figure. What happens to the brightness of bulb B1 when we close the switch S?

A galvanometer G has an internal resistance rg. An AMMETER is constructed by incorporating the galvanometer and an additional resistance Rs. Which one of the figures below is the most appropriate circuit diagram for the ammeter?

A galvanometer G has an internal resistance rg. A VOLTMETER is constructed by incorporating the galvanometer and an additional resistance Rs. Which one of the figures below is most appropriate circuit diagram for the voltmeter?

A resistor and a capacitor are connected in series across an ideal battery having a constant voltage across its terminals. At the moment contact is made with the battery a. The voltage across the capacitor is: b. The voltage across the resistor is:

an RC circuit is connected across an ideal DC voltage source through an open switch. The switched is closed at time t=0s. Which of the following statements regarding the circuit are correct?

A lightbulb is connected in the circuit shown in the figure with the switch S open and the capacitor uncharged. The battery has no appreciable internal resistance. Which one of the following graphs best describes the brightness B of the bulb as a function of time t after closing the switch?