Physics 2 Test One

centi

10^-2

From a single magnet, it is not possible to make an odd number of magnets.

False

Increasing the distance from a point charge by a factor of 2 will change the potential by a factor of how much?

It's cut in half

A negative charged plastic rod is brought close (but does not touch) A neutral metal sphere is connected to a ground. After waiting a few seconds the ground connection is removed (without touching the sphere) after that the rod is removed now the sphere is

Positively Charged

If you double the voltage across an ohmic resistor, how does the current through the resistor change?

The current will double.

Which of these statements about a household circuit is true:

The ground protects the user against faulty devices. As you add devices to a household circuit, the total current increases.

How are potential difference and electric field strength related for a constant electric field?

The magnitude of electric field is equivalent to the potential divided by the distance.

nano

10^-9

milli

10^-3

micro

10^-6

Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres by leaking off. When each of the spheres has lost half its initial charge, what will be the magnitude of the electrostatic force on each one?

1/4 F

kilo

10^3

Ammeter

A device used to measure current in a circuit

Voltmeter

A device used to measure voltage, or electrical potential energy difference

Which assumptions are unreasonable, or which premises are inconsistent?

A voltage of 480 V is unreasonably low for a transmission voltage.

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. It's first and the arrow is pointing down

If you applied a voltage across two points A and B, how would you calculate the electric field between those points?

Divide the voltage by the distance between two points.

If you increase the distance between the plates of a capacitor, how does the capacitance change?

Doubling the distance between capacitor plates will reduce the capacitance two-fold.

How is electric potential related to electric potential energy?

Electric potential is related to electric potential energy by the inverse of the unit charge at a given position in space.

Why does charge accumulate on the surface of a polarized dielectric, rather than distributing evenly throughout the volume of the material?

Excess charge in the volume of the dielectric is neutralized through polarization.

You move a compass in a circular plane around a planar magnet. The compass makes four complete revolutions. How many poles does the magnet have?

Four Poles

Under what conditions might a resistor material that normally follows Ohm's law become non-ohmic?

If the amount of current flowing though the material is too high, the resistor may heat up, creating a nonlinear relationship between current and voltage.

What effect does increasing the internal resistance of the source have on the load circuit?

Increasing internal resistance reduces the current that can be drawn from the source.

Define the fields of magnetism and electricity and state how are they are related.

Magnetism describes the attractive force between a magnetized object and a metal like iron. Electricity involves the study of electric charges and their movements. Magnetism is produced by a flow of electrical charges.

How can you verify whether a certain material is ohmic?

Make a resistor from this material and measure the current going through this resistor for several different voltages. If the current is proportional to the voltage, then the material is ohmic.

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.

Choose the battery as current source and set the number of wire loops to four. With a nonzero current going through the solenoid, measure the magnetic field strength at a point. Now decrease the number of wire loops to two. How does the magnetic field strength change at the point you chose?

The magnetic field strength decreases to half of its initial value when number of loops reduces from four to two.

A needle is magnetized by aligning it along the axis of a bar magnet and just outside the north pole of the magnet. Will the point of the needle that was closest to the bar magnet then be attracted to or repelled from the south pole of another magnet?

The needle will magnetize and the point of needle kept closer to the north pole will act as a south pole. Hence, it will repel the south pole of other magnet.

Toward which magnetic pole of Earth is the north pole of a compass needle attracted?

The north pole of a compass needle is attracted to the south magnetic pole of Earth, which is located near the geographic north pole of Earth

How does the polar character of water molecules help explain water's relatively large dielectric constant?

The polar character helps the water molecule orient itself in an electric field and move easily.

What is unreasonable about this result?

The transmission lines dissipate more power than they are supposed to transmit.

The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero

VW

What is the relationship between voltage and energy? More precisely, what is the relationship between potential difference and electric potential?

Voltage is the energy per unit charge at some point in space.

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

Galvanometer

a device that uses an electromagnet to measure electric current

Two lamps have different resistances. (a) If the lamps are connected in parallel, which one is brighter, the lamp with greater resistance or the lamp with less resistance? (b) If the lamps are connected in series, which one is brighter? Note that the brighter lamp dissipates more power.

a) lamp with less resistance; (b) lamp with greater resistance.

The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could

double the charge to 2Q

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

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?

it remains the same