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A_Edexcel GCSE Physics > SP10 - Electricity and Circuits ✓ > Flashcards

SP10 - Electricity and Circuits ✓ Flashcards

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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)
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2
Q

SP10a - Descirbe what a potential difference is.

A

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

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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.

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4
Q

SP10a - What are the two types of circuits?

A
  • Series: everything connected in one route
  • Parallel: many options for different routes.
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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
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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

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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.

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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.
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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
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10
Q

SP10c - What is current?

A
  • The flow of electrons
  • The rate of flow of charge
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11
Q

SP10c - What is the unit for charge?

A

C - Coulombs

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12
Q

SP10c - What is the equation linking charge and current?

A

Q = I x t

(Charge = Current x time)

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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)

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14
Q

SP10d - What is Ohm’s law?

A

V = I x R

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

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15
Q

SP10d - What is resistance?

A

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

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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 + ………..
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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
Q

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.

A
  • 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
Q

SP10f - What is the heating effect?

A
  • 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
Q

SP10f - Where is the heating effect useful?

A
  • 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
Q

SP10f - Describe what resistance is in terms of a metal’s structure.

A
  • 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
Q

SP10f - How can resistance be reduced in a circuit?

A
  • 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
Q

SP10f - What formula links energy, time and voltage?

A

E = I x t x V

Energy = Current x time x Voltage

31
Q

SP10g - What are the four formulae for power?

A
  • P = E/t
  • P = I x V
  • P = I² x R
  • P = V² ÷ R
32
Q

SP10g - How do you form the the equations that link Power and Resistance?

A
  • 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
Q

SP10h - What the voltage and frequency of and type of electricity that comes through mains supply?

A
  • 230V
  • 50Hz (changes diretion 50 times per second)
  • a.c
34
Q

SP10h - What are the differences between d.c and a.c?

A

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
Q

SP10i - Describe the five features of a 3-pin plug.

A
  • 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
Q

SP10i - How does an earth wire make an appliance safer?

A
  • 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
Q

SP10i - How does a fuse provide safety? (Describe this though it’s structure)

A
  • 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
Q

SP10i - How do you choose the best value for a fuse?

A
  • 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
Q

SP10i - What are circuit breakers and how do they work?

A
  • 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
Q

SP10i - Why are circuit breakers more advantageous than fuses?

A
  • 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
Q

SP10i - What are the colours of the earth, neutral and live wires?

A
  • Earth wire: Green and yellow
  • Neutral wire: Blue
  • Live wire: Brown
42
Q

SP10i - Why may fuses be more advantageous than circuit breakers?

A
  • Fuses are cheaper
  • More practical for small scale uses (e.g. small appliances)

A_Edexcel GCSE Physics (15 decks)

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