Topic 10 - Electricity and Circuits Flashcards

1
Q

SP10a - Describe the structure of an atom including features of the sub-atomic particles.

A
  • Proton and neutron in the nucelus, each with a relative mass of 1.
  • Protons have a charge of +1.
  • Electrons orbit in energy levels each with a charge of -1 and a relative mass of 1/1835 (negligible)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

SP10a - Descirbe what a potential difference is.

A

The force that pushes the electrons to flow around the circuit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

SP10a - What is conventional current?

A

What we refer to as the direciton of current form positive to negative. Opposite to the flow of electrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

SP10a - What are the two types of circuits?

A
  • Series: everything connected in one route
  • Parallel: many options for different routes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

SP10a - Why may parallel circuits be more beneficial?

A
  • If the circuit becomes incomplete along one path, the rest of the circuit can still continue to function. (e.g - Switches can be connected to different parts meaning lights in parallel to each other can be switched in and off individually)
  • If a bulb goes off, the rest of the circuit in parallel to this can still continue to function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

SP10b - What is the unit for current and how can it be measured?

A

Amps (Amperes). Measured using an ammeter which is attached in series to the circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

SP10b - What is the unit for potential difference and how can it be measured?

A

Volts. Measured using a voltmeter which is attached in parallel to the component you are measuring the potential difference of.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

SP10b - How does total current differ in parallel and series circuits?

A
  • S: The total current is the same at all points throughout the circuit
  • P: The total current gets split between the branches of the circuit, inversely proportionate to the resistance of the components in those branches.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

SP10b - How does potential difference differ in parallel and series circuits?

A
  • S: The p.d is different across different components, directly proportionate to the resistance of that component
  • P: The p.d is tha same at all points across the circuit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

SP10c - What is current?

A
  • The flow of electrons
  • The rate of flow of charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

SP10c - What is the unit for charge?

A

C - Coulombs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

SP10c - What is the equation linking charge and current?

A

Q = I x t

(Charge = Current x time)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

SP10c - What equation links energy and charge and how can this be changed to link energy to current?

A

E = Q x V (Energy = Charge x p.d)

since Q = I x t, this means that

E = I x t x V (Energy = Current x time x p.d)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

SP10d - What is Ohm’s law?

A

V = I x R

(p.d (V) = Current (A) x Resistance (Ω))

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

SP10d - What is resistance?

A

The force pushing back against p.d opposing and reducing the current.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

SP10d - How do you calculate the resistance in series and parallel circuits?

A
  • Series: Add up the resistance of all the components
  • Parallel: 1/RT = 1/R1 + 1/R2 + ………..
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

SP10d - What is key to remember about the size of the total resistance in series and parallel and series circuits?

A
  • S: It is greater than any of the individual resistances
  • P: It is smaller than all of the individual resistances
18
Q

SP10e - What does a IV graph for fixed resistor look like and why?

A
  • It is a straight diagonal line showing direct proportion.
  • This is because resistors are ohmic conductors.
  • The voltage is directly proportionate to the current.
19
Q

SP10e - What is an ohmic conductor?

A

A component in a circuit that follows Ohm’s rule of V=IxR

20
Q

SP10e - What does the gradient of an IV graph represent?

A

The inverse of the resistance (1/R)

21
Q

SP10e - What does a IV graph for diode look like and why?

A
  • A line that is nearly on the x-axis till it shoots up.
  • This is because a diode has an infinitely high resistance till a point where it has an infinitely low resistance
22
Q

SP10e - What does a IV graph for filament lamp look like and why?

A
  • An S shaped ‘curve’.
  • This is because the resistance of a lamp increases due to the temperature increase as it conducts electricity at a higher voltage
23
Q

SP10e - Describe what a graph for resistance of a thermistor would look like and why.

A
  • The x-axis would be temperature (°C) and the y-axis would be resistance (Ω)
  • As the temperature increases, the resistance decreases. This forms a negative curve in an L shape
  • This can be used to reduce the current in lower temperatures.
24
Q

SP10e - Describe what a graph for resistance of an LDR (Light-dependant resistor) would look like and why.

A
  • The x-axis would be light intensity (lux) and the y-axis would be resistance (Ω)
  • As the light intensity increases, the resistance decreases. This forms a negative curve in an L shape
  • This is used for lit up signs outside. In darker conditions (lower light intensity) bulbs don’t need to be as bright.
  • Thus, the resistance is higher to reduce the current and brightness
  • Resistance is high against the dark side #Starwars
25
SP10e CP - Describe your set-up for an experiment to compare the relationship of V=IxR in a resistor, and a filament lamp in parallel/series.
* Set up a series circuit with a power pack, an ammeter, a fixed resistor and a voltmeter in parallel to this. * Provide different voltages from the power pack. * For each voltage provided, note down the current - Replace the fixed resistor with a lamp and repeat * Set up the circuit from here so that there is a voltmeter attached in parallel to this. * Attach another lamp to the circuit with another voltmeter in parallel to this * Measure out the voltages and currents when different voltages are supplied * Move one of the bulbs with its voltmeter to a new branch forming a parallel circuit * Add an ammeter to each branch of the circuit * Now measure the voltage and current depending on the voltage provided
26
SP10f - What is the heating effect?
* The heating effect is when a circuit warms up due to the resistance in its wires. * Work is done against the resistance and so energy is transferred. * This is in the form of heating and dissipates into the surroundings
27
SP10f - Where is the heating effect useful?
* In appliances such as electric heaters and kettles where the aim is to use thermal energy, the heating effect is incredibly useful. * In these circuits, resistance tends to be high.
28
SP10f - Describe what resistance is in terms of a metal's structure.
* Current is the flow of electrons. * A metal is made of electrons flowing around positive metal ions * When the electrons are moving in the circuit, they can collide into these posistive metal ions. * These collisions are resistance and they transfer energy
29
SP10f - How can resistance be reduced in a circuit?
* Choosing a metal with a lower resistance * Using a thicker wire (more space for electrons to flow) * Using a shorter wire (less distance in which they can collide)
30
SP10f - What formula links energy, time and voltage?
E = I x t x V Energy = Current x time x Voltage
31
SP10g - What are the four formulae for power?
* P = E/t * P = I x V * P = I² x R * P = V² ÷ R
32
SP10g - How do you form the the equations that link Power and Resistance?
* We know that P = I x V and that V = I x R * If we substitue the V in the first equation we get P = I x I x R or P = I² x R * If we rearrange V = I x R we get I = V ÷ R * So if we substitute this in we get P = V x V ÷ I or P = V² ÷ R
33
SP10h - What the voltage and frequency of and type of electricity that comes through mains supply?
* 230V * 50Hz (changes diretion 50 times per second) * a.c
34
SP10h - What are the differences between d.c and a.c?
**d.c**: * Only one direction (positive to negative) * Electrons loose energy as they travel from positive to negative * A grpah showing the direction will only ever be on one side of the x-axis **a.c**: * Constantly switching direction (this is their frequency) * Electrons vibrate and pass on energy * A graph showing direction will contantly cross zero and over the x-axis A̶C̶/̶D̶C̶ ̶a̶r̶e̶ ̶a̶n̶ ̶A̶u̶s̶t̶r̶a̶l̶i̶a̶n̶ ̶r̶o̶c̶k̶ ̶b̶a̶n̶d̶ ̶f̶o̶r̶m̶e̶d̶ ̶i̶n̶ ̶S̶y̶d̶n̶e̶y̶ ̶i̶n̶ ̶1̶9̶7̶3̶ ̶b̶y̶ ̶b̶r̶o̶t̶h̶e̶r̶s̶ ̶M̶a̶l̶c̶o̶l̶m̶ ̶a̶n̶d̶ ̶A̶n̶g̶u̶s̶ ̶Y̶o̶u̶n̶g̶.̶
35
SP10i - Describe the five features of a 3-pin plug.
* Live wire: Connects the appliance to the generators at the power station providing 230V * Neutral wire: The return path to the power station and will be at 0V if circuit is correctly connected * Earth wire: Connects the metal parts of the appliance to a large spike of metal that pushes down and connects to the ground. Will be at 0V unless the circuit is incorrectly connected * Fuse: A Safety device usually 3, 5 or 13 A * Plastic casing: This electrical insulator allows you to safely hold the plug
36
SP10i - How does an earth wire make an appliance safer?
* If a wire comes loose and touches the metal part of the appliance, the electricity will beable to flow through this. * When a person touches it, the electricity can pass through the person to the ground. * This would give them an electric shock. * However the earth wire provides an easier way to travel to the ground. * As electrcity always takes the past of least resistance, it goes this way and the person doesn't get an electric shock
37
SP10i - How does a fuse provide safety? (Describe this though it's structure)
* A fuse is a glass tubing with a thin metal wiring that the electricity passes through. * A faulty appliance may draw too much current which would heat up and cause a fire. * However depending on the value of the fuse, it will melt once the current has reached a certain level and cause the circuit to be incomplete meaning current stops flowing through it
38
SP10i - How do you choose the best value for a fuse?
* Fuses are typically found in 3A, 5A, and 13A. * You want to pick one that has a current higher than what the current of the appliance is but not to high. * This way it will stop a fualty appliance but not a properly functioning one. * If an appliance has a current of 3A, you would pick a 5A fuse. 3A would be too low and 13A would be too high
39
SP10i - What are circuit breakers and how do they work?
* Circuit breakers are automatic swtiches that detect a rise in current and automatically switch off the supply safely. * They are an alternate to fuses.
40
SP10i - Why are circuit breakers more advantageous than fuses?
* They can just be turned back on rather than having to buy a new fuse * They work quicker. * You elliminate the risk of an accident occuring while the fuse is melting
41
SP10i - What are the colours of the earth, neutral and live wires?
* Earth wire: Green and yellow * Neutral wire: Blue * Live wire: Brown
42
SP10i - Why may fuses be more advantageous than circuit breakers?
* Fuses are cheaper * More practical for small scale uses (e.g. small appliances)