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Physics > Chapter 8 (8.1 - 8.7) Electricity > Flashcards

Chapter 8 (8.1 - 8.7) Electricity Flashcards

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1
Q

what is an electric charge

A

a property of matter that experiences a force when next to other charges or in an electric field.

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2
Q

when do masses attract

A

when they are of opposite charge

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3
Q

when do masses repel

A

when they are of same charge

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4
Q

what is a conductor
do they hold charge?

A

Materials that let electrons pass through them and have free electrons to carry charge.
Do not hold their charge

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5
Q

Materials that are conductors
2 examples

A

Metals - good conductors
Non-metals - poor conductors or don’t conduct at all. Except carbon

copper, iron

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6
Q

What is an insulator
easy method to charge

2 examples

A

Materials that can hardly conduct. Electrons are held to atoms tightly.

Can be charged easily via friction since aft electrons are transferred they stay there. That’s why they hold their charge.

Glass, rubber

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7
Q

What are semi conductors

A

Materials that are bad conductors when cold but good conductors when hot

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8
Q

What is earthing?
if its negatively charged?
if its positively charged?

A

process of neutralizing an object’s charge by connecting it to the earth and letting electrons flow in or out.

if -ve charge: excess electrons in the object flow to the earth

if +ve charge: electrons flow from the earth to the object

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9
Q

When is an object positively/negatively charged

A

When neg charges > positive
negatively charged

vice versa

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10
Q

Process of induction (giving an object a negative charge)

A
  1. get a positively charged rod near the object
  2. charges are separated - the electrons are attracted and protons are repelled
  3. connect an earthing wire - electrons flow into the object to neutralize the protons
  4. disconnect earthing wire
  5. take the positively charged rod away from the object
  6. now the sphere has more electrons than protons hence it has a negative charge now,
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11
Q

What is the SI unit of Charge
symbol

A

Coulomb (C)

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12
Q

what is an electrical field

A

region where charged particles experience a force. one charged particle will experience force from the other

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13
Q

Direction of electric field of a positive charge

A

Radially outward

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14
Q

Direction of electric field of a negative charge

A

Radially inward

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15
Q

How does charging by friction occur

A

When 2 objects are rubbed together, heat is generated. This heat energy gives the electrons enough energy to overcome their bond energies that are holding them to the atoms and allow them to travel to the other object.

The electrons and protons are no longer equal hence one object is +ve nad one is -ve

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16
Q

Charge of 1 electron

A

-1.6 * 10^-19 C

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17
Q

Charge of 1 proton

A

1.6 * 10^-19 C

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18
Q

Direction of electric field lines between 2 oppositely charged plates that are parallel to eachother

A

If the distance between plates is shorter compared to the length of the plate the curves of the electric fields on the edges reduces.

19
Q

what is current
notation and SI unit
formula with respect to charge

A

rate of flow of charge

charge/time=Q/T=coulumb/time

notation = I

SI unit = Ampere

20
Q

What is used to measure current
how is it connected
a special characteristic of it

A

Ammeter
Connected in series
Ideal ammeter - has 0 resistance

21
Q

How does current vary in a series circuit

A

it remains constant

22
Q

what is conventional current

A

is the flow of current from a positive terminal to negative

23
Q

what is potential difference
unit and formula with respect to charge

A

work done per unit charge
Volt (V)
V = W/Q where W = work done, Q = charge

24
Q

What is EMF

when is it the highest

A

Electromotive Force -
Amount of force/work done required to move a charge across the whole circuit.

The maximum potential difference

Highest when a battery is not connected to a circuit so p.d doesn’t drop.

25
Q

Formula for EMF

A

Sum of potential diff of all components in circuit

26
Q

What is used to measure voltage
how is it connected
special characteristic

A

Using a voltmeter
Connected in parallel
Ideal voltmeter - infinite resistance

27
Q

what is the definition of resistance and S.I unit

A

opposes the flow of current. Doesnt allow current to move freely

S.I unit is ohms

28
Q

what is ohms law

A

V = IR

v = potential diff
I = current
R = Resistance

29
Q

what are the factors affecting resistance

A

length
thickness of wire
temperature
material

30
Q

how does length affect resistivity

A

longer the wire greater the resistance

(directly proportional)

31
Q

how does thickness of the wire affect resistance

A

inversely proportional to the resistance.
thicker the wire lesser the resistance, as there are more particles for electricity to be conducted

32
Q

how does temperature affect the resistance

A

as temperature increases resistance increases in conductors
as temperature increases resistance decreases in semiconductors

33
Q

how does material affect the resistance
notation

A

as some materials help conduct the charge and others don’t conduct the charges as well.

notation: symbol rho - ρ

34
Q

Relation of resistance to the factors (formula)

A

resistance = resistivity x length/area

35
Q

What is a thermistor

give a use

A

Components that have high resistance when cold but low resistance when hot. Made of semiconductor materials

smoke detectors, thermostats

36
Q

what are some factors of ohms law

A

as voltage increases, resistance increases

37
Q

how would a graph between voltage and current look when resistance is constant

A

straight line

38
Q

how would a graph between voltage and current look when resistance is changing

A

curved

39
Q

in parallel circuit what happens to voltage and current

A

voltage is same
current differs

40
Q

how are the field lines of a positively charged particle drawn

A

arrows pointing outward from the particle

41
Q

how are the field lines of an negatively charged particle drawn

A

arrows pointing towards the object from the outside

42
Q

explain why energy losses are lower when voltage is higher

A

higher voltage = lower current (in power law/P=VI)
if current is lower then less energy is produced (E= VIT)
if less energy produced then less energy will be lost

43
Q

e.m.f definition

A

the total energy needed to transfer the charges from one terminal of the battery to the other

44
Q

in a series circuit what happens to voltage and current

A

current is same
voltage differs

Physics (25 decks)

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