Electromagnetism

Question 1

What do like charges do?

Answer 1

Repel

Question 2

What do unlike charges do?

Answer 2

Attract each other

Question 3

What is a conductor?

Answer 3

Allows charge to flow through it (electric current)

Question 4

What is an insulator?

Answer 4

A material which a charge flows poorly/not at all

Question 5

What is a semi-conductor?

Answer 5

Properties between those of conductors & insulators

Question 6

What causes charges in solids?

Answer 6

The mobile charge are electrons (negative) - lack of these negative charges = formation of positive charge

Question 7

Explain the Law of Conservation of Charge?

Answer 7

Total amount of charge in universe is constant - single charges cannot be created or destroyed - created or destroyed in pairs of opposite signs

Question 8

How can we induce a charge?

Answer 8

Place a negatively charged object close to a neutral object and the electrons will be forced out of the object into the ground - charge by induction

Question 9

What is the force between charges called?

Answer 9

The electrostatic force

Question 10

What is the unit for charge?

Answer 10

Coulomb

Question 11

How do we calculate electrostatic force?

Answer 11

Coulomb’s Law

F= 1/4πε0 x q1q2/r^2

ε0 Permittivity of Free Space

Question 12

What does charge always occur in multiples of?

Answer 12

Charge of electron

-1.6*^-19 C

Question 13

How do we calculate force due to several charges?

Answer 13

Add them

Question 14

Calculate electric field?

Answer 14

E = F/q

E=Q//4πε0r^2

Question 15

What way does an electric field run?

Answer 15

Fromm positive to negative (the direction in which a positive charge would travel)

Question 16

What increases as an area A approaches a charge Q?

Answer 16

No. of electric field lines, electric field & electric force

Question 17

What is the Electric flux?

Answer 17

Amount of field lines per unit area

Directly proportional to E , it orientation in respect to E, and size of A

Question 18

What creates an electric dipole?

Answer 18

Pair of equal but opposite charges at a fixed distance apart e.g. NaCl

Question 19

What happens to a dipole if direction of E changes rapidly?

Answer 19

Rotates rapidly clockwise & anticlockwise - experiences torque

Question 20

What is Gauss’ Law

Answer 20

the electric flux Φ across any closed surface is proportional to the net electric charge q enclosed by the surface; that is,

Φ = q/ε0,

Question 21

What must occur for a net flux to occur?

Answer 21

Flux lines moving out > flux line moving in

Question 22

What will a charge under E move from?

Answer 22

An area of high PE to lower PE - regions with electric potential difference?

Question 23

What is eclectic potential difference (Vab)?

Answer 23

The work necessary to move a unit charge between these points

Volts

Van = Wab/q

Question 24

Calculate electric potential using electric field?

Answer 24

Ed = V

the force on q = work done

SI unit for E is V/m

Question 25

How do batteries provide energy?

Answer 25

Via an electric potential difference/voltage - moves charge

Question 26

How is the current I described?

Answer 26

the direction at which a positive charge flows (+ to -)

Question 27

When does a current flow?

Answer 27

When the conducting path is complete

Question 28

Calculate electric current?

Answer 28

I = Q/t Amps I= velocity x area x density

Question 29

How to calculate resistance?

Answer 29

R = V/I = Ohms ability to resist flow of current

Question 30

What do resistors cause?

Answer 30

An electric potential difference

Question 31

Resistors in series?

Answer 31

R=R1 + R2

Question 32

Resistors in parallel?

Answer 32

1/R = 1/R1 + 1/R2 I = I1 + I2

Question 33

Power of electricity?

Answer 33

P = IV (watts) P=V^2/R P=I^2R

Question 34

What contributes to electric shocks?

Answer 34

Increased I

Question 35

How to measure the resistance of a material?

Answer 35

R = ρl/A

Question 36

Calculating electric field with Gauss' Law?

Answer 36

E = I/A I=flux

Question 37

How to Calculate capitance?

Answer 37

C = Q/V C= ε0A/d F Farads

Question 38

Energy stored in capacitor?

Answer 38

W = 1/2 CV^2

Question 39

Change in electric potential energy?

Answer 39

U=qV

Question 41

Do monopole magnets exist?

Answer 41

No

Question 42

What do similar poles do?

Answer 42

Repel

Question 43

What do unlike poles do?

Answer 43

Attract

Question 44

Where is the magnetic North Pole?

Answer 44

near the geographical south pole - slightly SW

Question 45

Where is the magnetic South Pole

Answer 45

near the geographical north pole - slightly NE

Question 46

Direction of magnetic field?

Answer 46

From north to south

Question 47

Do currents create magnetic fields?

Answer 47

Electric current causes a compass to move - magnetic field is parallel to wire

Question 48

What is the unit of magnetic field?

Answer 48

Tesla T

Question 49

Gauss' Law and magnetic flux?

Answer 49

The total magnetic flux from a dipole = 0

Question 50

What is a magnetic force on electric current?

Answer 50

Current carrying wire in presence of an external B, experience a force - perpendicular to I & B - Lorentz force F = BIL when I is perpendicular to B

Question 51

What is the force on a single charge?

Answer 51

F = BQv forced to move in circle - charge orbits the magnetic field line - Lorentz force provides centripetal force

Question 52

Calculate radius of motion?

Answer 52

r = mv / QB

Question 53

What is the principle of the electric motor?

Answer 53

Magnetic dipoles - some experience upward force & some downward - cause loop to rotate about its axis - experience torque

Question 54

Magnetic field for a single straight current carrying wire?

Answer 54

B= 2k I/R

Question 55

What type of magnetic force is present when two parallel wires run in the same direction?

Answer 55

Attractive

Question 56

If currents flow in opposite directions in parallel wires?

Answer 56

Repulsive force To calculate force on I2 remember F2=BI2L B is the magnetic field generated by I1 F2/L = 2k I1I2/d k=μ0/4π - magnetic permeability of free space

Question 57

What causes geomagnetism?

Answer 57

Flow of electrical currents in Earth's interior

Question 58

What causes magnetism in solids?

Answer 58

Electrons orbiting atomic nuclei in small magnetic fields created dipole magnetic fields - if there is a large number of these atoms aligned in the same direction - material has magnetic properties

Question 59

What is needed to induce I & V?

Answer 59

A rate of change in the current in the loop - change in magnetic flux

Question 60

Unit for magnetic flux?

Answer 60

Weber Flux = BA

Question 61

when is a loop at its max flux?

Answer 61

When it is parallel to B

Question 62

Are the I&V induced by magnetic flux constant?

Answer 62

No as the loop rotates sinusoidally - creating an alternating voltage & current

Question 63

How to calculate the magnitude of the induced voltage/ Faraday's Law?

Answer 63

V = change in flux / time