Final Exam Physics II Texas State University

A flat circular loop of wire of radius 0.50 m that is carrying a 2.0-A current is in a uniform magnetic field of 0.30 T. What is the magnitude of the magnetic torque on the loop when the plane of its area is perpendicular to the magnetic field?

0.00 N * m

An ideal solenoid 20 cm long is wound with 5000 turns of very thin wire. What strength magnetic field is produced at the center of the solenoid when a current of 10 A flows through it?

0.32 T

A straight wire carries a current of 10 A at an angle of 30◦ with respect to the direction of a uniform 0.30-T magnetic field. Find the magnitude of the magnetic force on a 0.50-m length of the wire.

0.75 N

A proton moving with a velocity of 4.0×104 m/s enters a magnetic field of 0.20 T. If the angle between the velocity of the proton and the direction of the magnetic field is 60◦, what is the magnitude of the magnetic force on the proton?

1.1 * 10^-15 N

An electron moves with a speed of 5.0 × 104 m/s perpendicular to a uniform magnetic field of magnitude 0.20 T. What is the magnitude of the magnetic force on the electron?

1.6 * 10^-15 N

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 20 cm. At what point between the two wires do they produce the same strength magnetic field?

16 cm from the 20 A wire

For the circuit shown in the figure, V = 60 V, C = 40 µF, R = 0.90 MΩ , and the battery is ideal. Initially the switch S is open and the capacitor is uncharged. The switch is then closed at time t = 0.00 s. At a given instant after closing the switch, the potential difference across the capacitor is twice the potential difference across the resistor. At that instant, what is the charge on the capacitor?

1600 µC ΔV(volts) + ΔV(resistor) + ΔV (capacitor) = 0 60V + (-ΔV) + (-2ΔV) = 0 ΔV = 20V ΔV(capacitor) = Q/C =(40µF)(20V)(-2) = 1600 µC

At what distance from a long straight wire carrying a current of 5.0 A is the magnitude of the magnetic field due to the wire equal to the strength of Earth's magnetic field of about 5.0 × 105 T?

2.0 cm

What is the magnetic moment of a rectangular loop having 120 turns that carries 6.0 A if its dimensions are 4.0 cm × 8.0 cm?

2.3 A*(m^2)

Two long parallel wires that are 0.40 m apart carry currents of 10 A in opposite directions. What is the magnetic field strength in the plane of the wires at a point that is 20 cm from one wire and 60 cm from the other?

6.7 µT

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

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 potential difference V across the resistor as a function of time t?

B

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 (120 V). If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct

The 100-W bulb grows brighter than the 50-W bulb. P = I ΔV In series, both bulbs get the same current. Thus whichever has the higher power rating has the higher ΔV and glows brighter.

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

increases