PHY131 Exam 2 CMU Questions
Correctly Answered.
Kirchoff's Law - CORRECT ANSWER Laws for analyzing circuits
Junction Rule - CORRECT ANSWER The sum of the currents entering a junction must equal the sum of
the currents leaving the junction
Loop (or Sum) Rule - CORRECT ANSWER The sum of the potential differences (voltage) around any
closed loop must be zero
Steps to solving loop problems - CORRECT ANSWER Assign currents and direction to each part of the
circuit (direction you just guess), apply the junction rule at each junction, apply the loop rule at each
CLOSED loop, you get a system of equations for the unknowns-which are the currents
V=-IR (negative = voltage decrease) - CORRECT ANSWER voltage when the direction around the loop is
the same as the current
V=+IR (positive = voltage increase) - CORRECT ANSWER voltage when the direction around the loop is
AGAINST the current
V=+Vb (positive = voltage increase) - CORRECT ANSWER Direction around the loop goes from the
negative terminal to the positive terminal
V=-Vb (negative = voltage decrease) - CORRECT ANSWER Direction around the loop goes from the
positive to the negative terminal
RC Circuits - CORRECT ANSWER Circuits with both a resistor and capacitor
0 - CORRECT ANSWER What is the initial charge AND voltage across a capacitor in an RC circuit?
, V=-Q/c - CORRECT ANSWER As charge builds up on the capacitor, what is the voltage change?
V=IR - CORRECT ANSWER What is the voltage change across the resistor?
equals the voltage of the battery - CORRECT ANSWER A capacitor will charge up until the voltage change
across the capacitor:
drops steadily (and exponentially) - CORRECT ANSWER As a capacitor charges, the current:
transcendental number - CORRECT ANSWER infinite numbers that never repeat
y=e^x - CORRECT ANSWER exponential function
time zero - CORRECT ANSWER When does the maximum current occur in an RC circuit?
seconds - CORRECT ANSWER units for time constant
out of the North Pole and into the south pole - CORRECT ANSWER What direction does the magnetic
field move?
attract - CORRECT ANSWER Opposite poles of a magnet:
repel - CORRECT ANSWER Likes poles of a magnet:
yes - CORRECT ANSWER Do all magnets always have a north and south pole
magnetic monopole - CORRECT ANSWER single magnetic pole or charge; no known examples that exist
Correctly Answered.
Kirchoff's Law - CORRECT ANSWER Laws for analyzing circuits
Junction Rule - CORRECT ANSWER The sum of the currents entering a junction must equal the sum of
the currents leaving the junction
Loop (or Sum) Rule - CORRECT ANSWER The sum of the potential differences (voltage) around any
closed loop must be zero
Steps to solving loop problems - CORRECT ANSWER Assign currents and direction to each part of the
circuit (direction you just guess), apply the junction rule at each junction, apply the loop rule at each
CLOSED loop, you get a system of equations for the unknowns-which are the currents
V=-IR (negative = voltage decrease) - CORRECT ANSWER voltage when the direction around the loop is
the same as the current
V=+IR (positive = voltage increase) - CORRECT ANSWER voltage when the direction around the loop is
AGAINST the current
V=+Vb (positive = voltage increase) - CORRECT ANSWER Direction around the loop goes from the
negative terminal to the positive terminal
V=-Vb (negative = voltage decrease) - CORRECT ANSWER Direction around the loop goes from the
positive to the negative terminal
RC Circuits - CORRECT ANSWER Circuits with both a resistor and capacitor
0 - CORRECT ANSWER What is the initial charge AND voltage across a capacitor in an RC circuit?
, V=-Q/c - CORRECT ANSWER As charge builds up on the capacitor, what is the voltage change?
V=IR - CORRECT ANSWER What is the voltage change across the resistor?
equals the voltage of the battery - CORRECT ANSWER A capacitor will charge up until the voltage change
across the capacitor:
drops steadily (and exponentially) - CORRECT ANSWER As a capacitor charges, the current:
transcendental number - CORRECT ANSWER infinite numbers that never repeat
y=e^x - CORRECT ANSWER exponential function
time zero - CORRECT ANSWER When does the maximum current occur in an RC circuit?
seconds - CORRECT ANSWER units for time constant
out of the North Pole and into the south pole - CORRECT ANSWER What direction does the magnetic
field move?
attract - CORRECT ANSWER Opposite poles of a magnet:
repel - CORRECT ANSWER Likes poles of a magnet:
yes - CORRECT ANSWER Do all magnets always have a north and south pole
magnetic monopole - CORRECT ANSWER single magnetic pole or charge; no known examples that exist
