Physics exam 1 review

Which one of the following quantities is equivalent to 1 W?

1 V • A

Which one of the following quantities is equivalent to 1 Ω?

1 V/A

For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?

1/(resistance)

Two ideal parallel-plate capacitors are identical in every respect except that one has twice the plate area of the other. If the smaller capacitor has capacitance C, the larger one has capacitance

2C

The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge?

400 V.

You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor. If you want to achieve the smallest possible resistance, you should attach the leads to the opposite faces that measure

5 cm × 8 cm.

An uncharged capacitor is connected in series with a resistor, a dc battery, and an open switch. At time t = 0 s, the switch is closed. Which of the graphs below best describes the charge Q on the capacitor as a function of time t?

A

Draw a circuit consisting of a battery connected to two resistors, R1 and R2, in series with each other and a capacitor C connected across the resistors.

A

Draw a circuit with a battery connected to four resistors, R1, R2, R3, and R4, as follows. Resistors R1 and R2 are connected in parallel with each other, resistors R3 and R4 are connected in parallel with each other, and both parallel sets of resistors are connected in series with each other across the battery.

A

Draw a circuit with two batteries, a resistor between them, and a capacitor in parallel with the resistor. The batteries are connected negative pole to positive pole.

A

Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates?

A.

A charged capacitor is connected in series with a resistor and an open switch. At time t = 0 s, the switch is closed. Which of the graphs below best describes the charge Q on the capacitor as a function of time t?

B

An uncharged capacitor is connected in series with a resistor, a dc battery, and an open switch. At time t = 0 s, the switch is closed. Which of the graphs below best describes the current I through the resistor as a function of time t?

B

Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?

B.

Four point charges Q of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?

D.

The length of a certain wire is kept same while its radius is doubled. What is the new resistance of this wire?

It is reduced by a factor of 4.

Three identical capacitors are connected in series across a potential source (battery). If a charge of Q flows into this combination of capacitors, how much charge does each capacitor carry?

Q

Three identical capacitors are connected in ->parallel to a potential source (battery). If a charge of Q flows into this combination, how much charge does each capacitor carry?

Q/3

You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct?

The 50-W bulb glows more brightly than the 100-W bulb.

The lamps in a string of decorative lights are connected in parallel across a constant-voltage power source. What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.)

The brightness of the lamps will not change appreciably.

A conductor is placed in a steady external electric field. Which of the following statements are correct for this situation? (There could be more than one correct choice.)

The electric field just outside the surface of the conductor is perpendicular to the surface.

Which statements must be true about the surface of a charged conductor in which no charge is moving? (There could be more than one correct choice.)

The electric potential is constant over the surface.

A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Which statement is true?

The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus.

Four unequal resistors are connected in a parallel with each other. Which one of the following statements is correct about this combination?

The equivalent resistance is less than that of the smallest resistor.

Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 µC of charge and bead B carries 1 µC. Which one of the following statements is true about the magnitudes of the electric forces on these beads?

The force on A is exactly equal to the force on B.

When two or more different capacitors are connected in parallel across a potential source (battery), which of the following statements must be true? (There could be more than one correct choice.)

The potential difference across each capacitor is the same.

The figure shows electrons passing through a resistor. The arrow shows the direction in which the electrons are moving. Which of the following statements are correct? (There could be more than one correct choice.)

The speed of the electrons at point b is the same as it is at point a.

X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?

X is negative and Y is positive.

An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field?

Z.

As a proton moves in a direction perpendicular to the electric field lines

both its electric potential and electric potential energy remain constant.

When a current flows through an ionic liquid such as salty water, the moving charges are

both positive and negative ions.

If a quantity you calculated has units of A • s, what is that quantity?

charge

As more resistors are added in series to a constant voltage source, the power supplied by the source

decreases.

The electron-volt is a unit of

energy.

If the electric potential at a point in space is zero, then the electric field at that point must be

impossible to determine based on the information given.

Suppose you have two capacitors and want to use them to store the maximum amount of energy by connecting them across a voltage source. You should connect them

in parallel across the source.

When the current through a resistor is increased by a factor of 4, the power dissipated by the resistor

increases by a factor of 16.

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electric potential energy of the electron due to the proton.

increases.

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

increases.

A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod

is repelled by the sphere

As an electron moves in the direction the electric field lines

it is moving from high potential to low potential and gaining electric potential energy.

As a proton moves in the direction the electric field lines

it is moving from high potential to low potential and losing electric potential energy.

You buy a AA battery in the store, and it is marked 1.5 V. If this marking is strictly accurate, while this battery is fresh

its terminal voltage will be less than 1.5 V when it is used in a circuit.

When a current flows through a metal wire, the moving charges are

only electrons.

When unequal resistors are connected in series across an ideal battery,

the current flowing in each is the same.

When different resistors are connected in parallel across an ideal battery, we can be certain that

the potential difference across each is the same.

Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one?

they remain the same

A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in parallel with the first one, the time constant of the new RC circuit will be

three times a large as before.

Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is

zero.