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1.1/1.2 Physics > Electromagnetism > Flashcards

Electromagnetism Flashcards

1
Q

What do like charges do?

A

Repel

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2
Q

What do unlike charges do?

A

Attract each other

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3
Q

What is a conductor?

A

Allows charge to flow through it (electric current)

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4
Q

What is an insulator?

A

A material which a charge flows poorly/not at all

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5
Q

What is a semi-conductor?

A

Properties between those of conductors & insulators

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6
Q

What causes charges in solids?

A

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

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7
Q

Explain the Law of Conservation of Charge?

A

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

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8
Q

How can we induce a charge?

A

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

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9
Q

What is the force between charges called?

A

The electrostatic force

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10
Q

What is the unit for charge?

A

Coulomb

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11
Q

How do we calculate electrostatic force?

A

Coulomb’s Law

F= 1/4πε0 x q1q2/r^2

ε0 Permittivity of Free Space

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12
Q

What does charge always occur in multiples of?

A

Charge of electron

-1.6*^-19 C

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13
Q

How do we calculate force due to several charges?

A

Add them

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14
Q

Calculate electric field?

A

E = F/q

E=Q//4πε0r^2

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15
Q

What way does an electric field run?

A

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

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16
Q

What increases as an area A approaches a charge Q?

A

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

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17
Q

What is the Electric flux?

A

Amount of field lines per unit area

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

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18
Q

What creates an electric dipole?

A

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

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19
Q

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

A

Rotates rapidly clockwise & anticlockwise - experiences torque

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20
Q

What is Gauss’ Law

A

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,

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21
Q

What must occur for a net flux to occur?

A

Flux lines moving out > flux line moving in

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22
Q

What will a charge under E move from?

A

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

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23
Q

What is eclectic potential difference (Vab)?

A

The work necessary to move a unit charge between these points

Volts

Van = Wab/q

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24
Q

Calculate electric potential using electric field?

A

Ed = V

the force on q = work done

SI unit for E is V/m

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25
Q

How do batteries provide energy?

A

Via an electric potential difference/voltage - moves charge

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26
Q

How is the current I described?

A

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

27
Q

When does a current flow?

A

When the conducting path is complete

28
Q

Calculate electric current?

A

I = Q/t Amps

I= velocity x area x density

29
Q

How to calculate resistance?

A

R = V/I = Ohms

ability to resist flow of current

30
Q

What do resistors cause?

A

An electric potential difference

31
Q

Resistors in series?

32
Q

Resistors in parallel?

A

1/R = 1/R1 + 1/R2

I = I1 + I2

33
Q

Power of electricity?

A

P = IV (watts)

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

34
Q

What contributes to electric shocks?

A

Increased I

35
Q

How to measure the resistance of a material?

36
Q

Calculating electric field with Gauss’ Law?

A

E = I/A

I=flux

37
Q

How to Calculate capitance?

A

C = Q/V

C= ε0A/d

F Farads

38
Q

Energy stored in capacitor?

A

W = 1/2 CV^2

39
Q

Change in electric potential energy?

41
Q

Do monopole magnets exist?

42
Q

What do similar poles do?

43
Q

What do unlike poles do?

44
Q

Where is the magnetic North Pole?

A

near the geographical south pole - slightly SW

45
Q

Where is the magnetic South Pole

A

near the geographical north pole - slightly NE

46
Q

Direction of magnetic field?

A

From north to south

47
Q

Do currents create magnetic fields?

A

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

48
Q

What is the unit of magnetic field?

49
Q

Gauss’ Law and magnetic flux?

A

The total magnetic flux from a dipole = 0

50
Q

What is a magnetic force on electric current?

A

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

51
Q

What is the force on a single charge?

A

F = BQv

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

52
Q

Calculate radius of motion?

A

r = mv / QB

53
Q

What is the principle of the electric motor?

A

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

54
Q

Magnetic field for a single straight current carrying wire?

55
Q

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

A

Attractive

56
Q

If currents flow in opposite directions in parallel wires?

A

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

57
Q

What causes geomagnetism?

A

Flow of electrical currents in Earth’s interior

58
Q

What causes magnetism in solids?

A

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

59
Q

What is needed to induce I & V?

A

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

60
Q

Unit for magnetic flux?

A

Weber

Flux = BA

61
Q

when is a loop at its max flux?

A

When it is parallel to B

62
Q

Are the I&V induced by magnetic flux constant?

A

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

63
Q

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

A

V = change in flux / time

1.1/1.2 Physics (8 decks)

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