Electricty and Electromagnetism

Question 1

Voltage (Electric Potential Difference) (V)

Answer 1

amount of energy per unit charge
EVQ

Question 2

1 Volt equals

Answer 2

1 J/C

Question 3

Power (P)

Answer 3

W
EPt

Question 4

1 Watt equals

Answer 4

J/s

Question 5

Resistance (R)

Answer 5

Ohms

Question 6

1 Ohm equals

Answer 6

1 V/A

Question 7

Formations of PIV

Answer 7

P=I^2R
P=V^2/R

Question 8

1 Amp. equals

Answer 8

1 C/s

Question 9

Charge (Q)

Answer 9

Coulomb

Question 10

Conventional Current

Answer 10

comes out of +ve terminal to -ve terminal in a battery

Question 11

Kirchoff’s Current Law

Answer 11

@ any junction pt. in a circuit the current equals the total current
SPLITS like Water

Question 12

Kirchcoff’s Voltage Law

Answer 12

Around ANY path in a circuit the total voltage equals the sum of voltages in that path
ADDS in any path

Question 13

Ohm’s Law

Answer 13

Total resis. is the ratio of volt. across battery and current being drawn
VIR

Question 14

Series Circuit Rules

Answer 14

I=I=I=I (KCL)
V=V+V+V (KVL)
R=R+R+R (Ohms)

Question 15

Parallel Circuit Rules

Answer 15

V=V=V=V (KVL)
I=I+I+I (KCL)
1/R = 1/R +1/R + 1/R

Question 16

Magnestism

Answer 16

opposite poles attract, similar repel

Question 17

Magnetic Force

Answer 17

varies inversely
fm = 1/d^2
so if d is doubled then fm is cut by 1/4

Question 18

Bar magnet

Answer 18

straight lines coming out of poles into N, out of south and circle along that go N to S

Question 19

Horseshoe magnet

Answer 19

strongest in between the horseshoe
and curve at the ends

Question 20

Basic Principal of Electromagnetism

Answer 20

CURRENT creates MAGNETIC FIELDS

Question 21

Right hand rule for straight conductor

Answer 21

• circular magnetic field lines
• thumb to current, curl in direction of mag. field

Question 22

Right hand rule for solenoid (coil)

Answer 22

• same mag. field as bar magnet
• coil fingers to the conventional current and thumb points to north

Question 23

3 factors that affect magnetic field strength

Answer 23

1. Amount of current
2. # of coils
3. Core material

Question 24

Ferromagnetic

Answer 24

easily magnetized
- inc. strength of electromagnet
- “soft irons” such as iron, cobalt and nickel

Question 25

Paramagnetic

Answer 25

- rarely magnetized - slight inc. electromag strength - ie air & aluminum

Question 26

Diamagnetic

Answer 26

- not magnetized - dec. strength of electromagnet - ie. copper & water

Question 27

Motor Principle

Answer 27

a CURRENT carrying conductor placed IN a MAGNETIC FIELD feels a magnetic force and MOVES - Force is always PERPENDICULAR to current and field

Question 28

Right hand rule for Motor principle

Answer 28

Finger - field Thumb - current Palm - force

Question 29

Parts of DC Motor

Answer 29

- armature (spins) - external magnet (no spin) - brushes (no spin) - split ring commutator (spins)

Question 30

Generator Effect

Answer 30

MOVING MAGNETS creates INDUCED CURRENT

Question 31

Lenz's Law

Answer 31

INDUCED CURRENT creates INDUCED MAGNETIC FIELD that OPPOSES MOTION

Question 32

Electric DC Motor

Answer 32

Moves since Lenz's Law that a current in the coil armature is in a magnetic field between the external magnets so MOVES - every 180 or half rotation the polarity of the armature switches

Question 33

DC Generator

Answer 33

No battery connected only circuit (unlike motor) - you or something like water wheel must rotate the armature - direct current - only runs in one direction

Question 34

AC Generator

Answer 34

SLIP Ring Commutators Outer slip only touches top brush Inner slip only touches bottom brush - the slip it goes into is where it goes into circuit - every revolution the current switches directions - 60 Hz

Question 35

4 factors that inc. output from generators

Answer 35

- more coils - stronger external magnets - spin faster - changing the core material to high agnetic permeability

Question 36

Transformer

Answer 36

device that CHANGES VOLTAGE - since easier to transfer electrical energy at low current and high potential

Question 37

Step- Up Transformer

Answer 37

- inc. voltage - @ generating stations - more coils on secondary coil

Question 38

Step-Down Transformer

Answer 38

- dec. voltage - @ residential area - more coils on primary coil