Download THE 10 OHM (IN PARALLEL THEY HAVE THE SAME VOLTAGE

Fundamentals of Physics 2nd Semester Final Review
1. In order for current to flow in a circuit, you must have
Potential (voltage) Difference and a conducting path
2. Electrical resistance is measured in
OHMS
Electrical current is measured in
AMPS
Electrical potential is measured in
VOLTS
3. When resistors are put in series next to each other does the resistance go up or down?
UP
What about parallel?
DOWN
5. If you put two light bulbs in series the total current will be HALF as much as if there was just one bulb.
6. If you put two light bulbs in parallel the total current will be TWICE as much as if there was just one bulb.
7. When one light bulb in a series circuit containing several lights is unscrewed then what happens to the other
bulbs? THEY GO OUT
8. When one light bulb in a parallel circuit containing several lights is unscrewed then what happens to the
other bulbs? NOTHING
9. (T or F) In a simple parallel circuit
current through each branch is always the same. F
voltage across each branch is always the same. T
the value of each resistor is the same. F
the circuit won't work unless there is a fuse in it. F
10. Is your microwave hooked up in series or in parallel to your refrigerator?
PARALLEL
11. What are Fuses and circuit breakers? How do they work?
THEY ARE SAFTEY DEVICES THAT BREAK THE CIRCUIT WHEN THE CURRENT
GETS TOO HIGH TO PREVENT THE WIRES FROM HEATING UP AND CAUSING
FIRES
12. A ten ohm resistor and a 20 ohm resistor are hooked in series. Which has a greater current?
SAME (IN SERIES THE CURRENT IS CONSTANT)
13. What if they were hooked up in parallel?
THE 10 OHM
(IN PARALLEL THEY HAVE THE SAME VOLTAGE AND I=V/R SO
SMALL R GETS THE LARGER CURRENT)
14. The total resistance of a 10-ohm resistor and a 70-ohm resistor in series is
10+70 = 80 OHMS
15. The total resistance of a 5-ohm resistor and a 20-ohm resistor in parallel is
1/5 + 1/20 = 4/20+1/20 =5/20=1/4
4 OHMS
16. A 75-W light bulb and a 120-W light bulb are both connected in parallel to a 120-V outlet. Which light bulb
has more current in it?
P=VI
120 W
17. An ampere is a unit of CURRENT
18. What are a few ways to create a voltage?
BATTERIES, GENERATORS, CAUSING STATIC.
19. Why a bird can perch harmlessly on bare high voltage wires
ALL THE SAME VOLTAGE. NO CONDUCTING PATH TO LOW VOLTAGE!
20. Does a battery supply AC or DC?
DC
21. Where do the electrons come from in a circuit?
a.
THEY ALREADY EXIST IN THE WIRES AND OTHER PARTS OF THE CIRUIT.
THEBATTERY JUST PUSHES THEM.
22. When an 12-V battery is connected to a resistor, 4 A of current flows in the resistor. What is the resistor's
value?
I=V/R
4=12/R
R=3 OHMS
23. How much power is used by a 12.0-V car battery that draws 2 A of current?
P=VI =12(2)=24
24. How can you induce a current in a loop of wire using a magnet.
MOVE THE MAGENT NEAR THE WIRE OR MOVE THE WIRE NEAR THE
MAGNET.
25. What is it called when you of induce voltage by changing the magnetic field around a conductor?
ELECTROMAGNETIC INDUCTION
26. If you spin a coil in a stationary magnetic field, what kind of device have you made?
GENERATOR
27. Where does the energy come from when a generator makes a current?
FROM THE MECHANINCAL (KINETIC ENERGY) OF WHATEVER IS SPINNING THE
COIL OR MAGNET
28. The charge of an electron is NEGATIVE. The charge of a proton is POSITIVE
29.
30.
31.
32.
Two like charges REPELL
Protons and electrons ATTRACT
What happens to electrical forces as charges are moved apart? THE FORCE GETS SMALLER
Coulomb's law says that the force between any two charges is directly/inversely proportionate to THE
SQUARE OF THE DISTANCE
33. Two charges are separated by a certain distance. If the magnitude of each charge is doubled, the force on each
charge is POSITIVE If the distance is doubled the force is CUTS DOWN TO 1/4.
34. If you rub a plastic rod with rabbit fur and the fur becomes positively charged, the rod becomes NEGATIVE
35. A positively charged rod is brought near a metal can that rests on a wood table. You touch the opposite side of
the can momentarily with your finger. The can is then NEGATIVE (THE NEGATIVES GET PULLED
IN)
36. What is electrical polarization and when does it happen? POLARIZATION IS THE SEPERATION OF
CHARGES THAT HAPPENS WHEN A CHARGED OBJECT IS BROUGHT CLOSE TO AN
UNCHARGED ONE)
37. The reason a charged balloon will stick to a wall is that THE LIKE CHARGES GET REPELLED AWAY
AND THE OPPISITE CHARGES GET PULLED CLOSE (POLARIZATION) SO THERE IS MORE
ATTRATION FROM THE OPPISITE CHARGE!
38. Two positive charges held near each other are released. As they move, the force on each particle GOES
DOWN (BECAUSE THEY MOVE APART BECAUSE THEY REPEL)
What if it was a positive and a negative? IT WOULD GO UP BECAUSE THEY MOVE TOGETHER
39. The unit of charge is COULOMBS
The unit of force is NEWTONS
40. Two charges of 10 C each are separated by 3 meters. What is the force they exert on each other? K = 9 x
109 Nm2/C2
F=KQq/R2= (9 x 109)(10)(10)/32=1011N
41. The source of all magnetic fields is MOVING CHARGES
42. Which will deflect moving electric charges? ELECTRICAL OR MAGNETIC FIELDS WILL DEFLECT
CHARGES
43. If the north pole of one magnet is brought near the south pole of another magnet, the poles will ATTRACT
But a north pole brought near another north pole will REPELL
44. (T or F) If you break a bar magnet in half, each half will have just one pole. FALSE EACH HALF WILL
HAVE A NORTH AND A SOUTH POLE
45. What does a compass do in a magnetic field? IT LINES UP WITH THE FIELD
46. Where is the magnetic field of a permanent magnet the strongest? NEAR THE POLES
47. When is there a magnetic field around a wire? WHENEVER THERE IS CURRENT IN THE WIR
48. How do you to make an electromagnet? RUN CURRENT IN THE WIRE
49. Which pole of a compass needle points to the north pole of a magnet? SOUTH