Name:_____________________________
Per:__________
Date:____________
Physics Electricity & Magnetism Review
1) Why does the magnet fall slowly through the copper pipe (in class)?
Electromagnetic Induction causes the magnet to slow down because a changing magnetic field causes a current
to flow in the copper pipe to create a temporary magnetic field in the opposite direction.
2) List 3 ways you could increase the amount of voltage produced in your rip-cord generator:
1) Increase the rotational speed
2) Add alternating magnets
3) Changing the location of the core
3) How (specifically) does a speaker work (we will build one on Tuesday)?
The alternating current in wrapped wire causes a changing magnetic field which attracts and repels the
stationary magnet. This vibrates the membrane (paper plate) and the sound is made from the vibrations.
4) How (specifically) does a motor work (see class example)?
Current passed through a coil of wire, creating a temporary magnetic field that rotated near another magnet and caused the
armature to spin.
5) What are 3 things an electromagnet can do that a permanent magnet cannot?
1) Turn the electromagnet on or off
2) Increase or decrease the strength of the electromagnet
3) Change the poles (polarity) of the electromagnet
Solve for the following circuits:
RT
8.0
R1
24.0
VT
6.0V
4.0
12.0
R2
8.0
V1
6.0V
IT
4.0
V2
2.0V
I1
0.25A
R3
V3
1.0V
I2
0.25A
12.0
3.0V
I3
0.25A
0.25A
RT
R1
2.0
VT
3.0V
18.0
R2
18.0
V1
R3
3.0
V2
9.0
V3
3.0 9.0
3.0V
IT
3.0V
I1
1.5A
3.0V
I2
0.17A
3.0V
I3
1.0A
0.33A
8) Draw the shape of the magnetic field lines, including direction with arrows, for the following bar magnet below.
See survey class notes for 3/23/15
N
S
9) Consider the wiring in your home… What type of circuit is it? _______Parallel_____
10) The type of current in a battery is ___DC___ and outlets in your home are ___AC_____
11) The voltage of a single cell is ___1.5 DCV____ and typical US outlets are ____120 ACV________
12) In a parallel circuit, the resistor with less resistance has more / less (circle one) current.
13) Draw the schematic diagram of a flashlight including all 3 parts. Label + & - sides of the battery!
See survey class notes for 3/23/2015
14) If a battery puts out 9.0V and the bulb has a resistance of 40.0Ω, what is the current in the circuit?
I=V/R=(9.0)/(40.0)=0.225= 0.22A (even-odd rule, round nearest even when half-way)
15) If a single 1.5V cell is connected to a 34kΩ resistor, how much current will it draw?
I=V/R=(1.5)/(34000)= 0.000044A = 4.4 x 10-5A
16) If a TV draws 150mA of current when plugged into an outlet of 120V, how much resistance does it have?
R = V/I = (120)/(0.150A) = 800Ω = 8.0 x102 Ω
17) A 1300W hairdryer will draw how much current (when plugged into 120V)? (P=IV)
I = P/V = (1300)/(120) = 10.833 = 11A
18) What is the resistance of the previous hairdryer?
R =V/I = (120)/(11) =10.909 = 11Ω
19) Current always travels which way in a DC circuit?
From positive to negative
20) If I were to walk in a straight line following the green tip of my compass needle, where would I eventually end up?
Geographic North pole, which is a south magnetic pole
21) A compass works because the earth acts as a giant _____Magnet_______
22) As a current passes through a straight wire, describe the path of the magnetic field around the wire.
The magnetic field goes in a circle around the wire
23) Describe how you measure the resistance in a circuit.
All of the circuit is disconnected and you use the meter on the Ohm setting and measure across the resistor
24) Describe how you measure the current in a circuit.
The circuit has to be open (switch is open) and you use the meter on DCA and measure across the switch.
25) Describe how you measure the voltage in a circuit.
Close the switch and measure across the battery or bulb or resistor.
26) In a series circuit, what always stays the same?
In a series circuit, the current stays the same.
27) In a parallel circuit, what always stays the same?
In a parallel circuit, the voltage always stays the same.
28) In a series circuit, as you add more resistors what happens to the equivalent resistance?
In a series circuit, adding resistors increases the total resistance.
29) In a parallel circuit, as you add more resistors what happens to the equivalent resistance?
In a parallel circuit, adding resistors decreases the total resistance.
30) Explain how charge separation occurs .
The electrons in an object move around (attract or repel) from another charged source.