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(A) Physics > P3 > Flashcards

P3 Flashcards

1
Q

What is electric charge

A

A property of a particle - can be positive or negative

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2
Q

What happens when you rub two insulators together

A

Electrons can be transferred
One insulator ends up with more electrons than the other giving it an overall negative charge

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3
Q

What is static electricity

A

The charge insulating objects acquire due to the transfer of electrons

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4
Q

How do you discharge an object

A

Connect it to something that allows a current to flow (conductor)

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5
Q

What are sparks

A

A flow of current and lightning through the airb

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6
Q

What is an electric field

A

A field around a charged particle that will attract or repel another charged object even if they are not touching

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7
Q

What is current and how do you meausrebit

A

Current is the rate of flow of charged particles

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8
Q

How do you make current flow

A

You need a complete circuit containing a cell or battery

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9
Q

How does the rope model, model electricity

A

A person pulling the rope is a battery and the movement of the rope is the charge

The person griping the rope represents a circuit component

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10
Q

What is conventional current

A

Positive to negative flow of charge

This is opposite to electron flow

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11
Q

How do you calculate charge

A

Charge is measured in Coulombs

Charge = current. × time

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12
Q

What is potential difference

A

A difference in electrical potential produced by the separation of charge

1v shows 1J of energy transferred per coulomb of charge that is moving through the circuit

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13
Q

What happens when you apply p.d to two sides of a wire

A

An electric field is created quickly, so the charged electrons move straight away

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14
Q

In a diagram what end of a cell/battery is positive and which is negative

A

Positive - the longer line
Negative - the smaller line

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15
Q

How d measure the energy transferred (electrical working) by p.d

A

P.d (volts) × charge

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16
Q

What is a series circuit

A

A circuit with one loop
The current is the same throughout all of this loop

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17
Q

How do you measure amps

A

Using an ammeter

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18
Q

How do you measure volts

A

A voltmeter

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19
Q

What does a voltmeter measure

A

Volts - the rise in potential across a cell or battery / the drop in potential across a component

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20
Q

How do voltmeters need to be set up in order to show the p.d of a component

A

Connected to both sides of the component

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21
Q

How do you find the voltage at the cell of a series circuit

A

Add all the voltage (from the components) together

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22
Q

Why is the voltage across a wire zero

A

There is a very little potential difference across wires

23
Q

What is a parallel circuit

A

Having two or more loops

24
Q

What is resistance

A

A measure of how easy it is for current to flow

25
Q

How do you calculate restistance

A

Using

Resistance = p.d ÷ current
R= v/I

26
Q

How do you calculate p.d

A

V = I×R

Amps is I

27
Q

Why does the resistance of some components change

A

Metals are made of positively charged ions in a regular shape
These ions are formed when electrons leave the outer shell - and these delocalised electrons move throughout the metals structure

Resistance is produced when electrons collide with the ions in a lattice. This is why the resistance of some components change with current

(Greater current = faster electrons = more collisions)

28
Q

What is a variable resistor

A

A resistor that can change the amount of wire or other resisting material - to increase or decrease a circuit resistance

29
Q

Do longer wires have a greater or lower resistance

A

The longer the wire the greater the resistance

30
Q

What can you use a p.d and current graph to calculate

A

The resistance

31
Q

What does the graph of a wire or resistor look like

A

It is a linear graph where the p.d is directionally proportional to the current

32
Q

What is ohms law

A

The current is directly proportional to the potential difference if the current doesn’t change
The resistance is constant

33
Q

What does a p.d current graph of a wire look like

A

Its a non linear graph

This is because the wire gets hot, so the resistance is not constant

34
Q

How do filament lamps work

A

Electrons in a wire collide with ions in a wire.
The ions vibrate more as the temperature gets hotter
(As the temp increases a glow is produced)

As that happens there are more collisions
The wire heats up more.
The current increases qs p.d increases but at a slower rate

35
Q

What does the current p.d graph of a diode look like

A

Diodes only work in positive values, so when charge in negative no current is produced

When you apply a small amount of positive p.d the current suddenly increases

36
Q

How is an LED connected to a battery

A

The long leg of an LED is connected to a battery

37
Q

What is a thermistor

A

A circuit component that has a resistance which depends on temperature

Its a semi conductor

Resistance decreases when temp increases

(Explanation - not needed)
Increased temp = increased conduction = increased flow of electrons

38
Q

How does the resistance change with temperature

A

As the temperature increases the resistance increases

39
Q

How could a thermistor be used in a circuit with a fan

A

As the outside temperature increases the resistance increases. This means the current must be increasing (to keep p.d the same)

This current can then activate the fan (if the fan only turns on above a certain current)

40
Q

What is an LDR

A

A light dependent resistor

Its resistance depends on the light intensity

41
Q

How does the resistance of an LDR change with LI

A

As light intensity increases, more electrons are released by the semiconductor so resistance decreases

(Same for Thermostor)

42
Q

How do you calculate net resistance

A

It is the total resistance in a circuit
Adding components in series increases the net resistance

Adding components in parallel decreases the net resistance

43
Q

What are sensing circuits

A

A circuit which contains a conductor with a resistance that changes with a change to the environment

44
Q

How do you calculate electrical power

A

Power = p.d × current

Power = resistance × current^2

45
Q

How do you calculate energy transferred (using power)

A

Power × time

46
Q

What happens to current and voltage in series circuits

A

Current - the current is the same across the whole cell

P.d (voltage) - The p.d is split across each component in the circuit.
This voltage adds up to the p.d across the battery

47
Q

What is current and p.d like in parallel circuits

A

Current - The current in each branch (loop) adds up to the current at the battery

P.d - the total voltage in each loop is equal to the voltage at the battery

48
Q

What is direct current

A

Current in a cell moving in one direction

49
Q

What is alternating current

A

Current in a circuit that is constantly changing at a specific frequency

50
Q

What is the voltage and frequency of alternating current in the uk

A

Frequency - 50 hertz
Voltage - 230v

51
Q

What device is used to view changing p.d

A

An oscilloscope

52
Q

What is an oscilloscope used for (p3)

A

It can be used to measure alternating current.
It shows a graph of p.d against time, where the p.d is constantly changing between positive and negative values

53
Q

How do you calculate resistance in parallel

A

Total resistance = 1/r1 + 1/r2 ….

(A) Physics (10 decks)

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