SP10 - Electricity and Circuits ✓
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SP10a - Describe the structure of an atom including features of the sub-atomic particles.
• 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)
SP10a - Descirbe what a potential difference is.
The force that pushes the electrons to flow around the circuit.
SP10a - What is conventional current?
What we refer to as the direciton of current form positive to negative. Opposite to the flow of electrons.
SP10a - What are the two types of circuits?
• Series: everything connected in one route • Parallel: many options for different routes.
SP10a - Why may parallel circuits be more beneficial?
• 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
SP10b - What is the unit for current and how can it be measured?
Amps (Amperes). Measured using an ammeter which is attached in series to the circuit
SP10b - What is the unit for potential difference and how can it be measured?
Volts. Measured using a voltmeter which is attached in parallel to the component you are measuring the potential difference of.
SP10b - How does total current differ in parallel and series circuits?
• 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.
SP10b - How does potential difference differ in parallel and series circuits?
• 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
SP10c - What is current?
• The flow of electrons • The rate of flow of charge
SP10c - What is the unit for charge?
C - Coulombs
SP10c - What is the equation linking charge and current?
Q = I x t (Charge = Current x time)
SP10c - What equation links energy and charge and how can this be changed to link energy to current?
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)
SP10d - What is Ohm’s law?
V = I x R (p.d (V) = Current (A) x Resistance (Ω))
SP10d - What is resistance?
The force pushing back against p.d opposing and reducing the current.
SP10d - How do you calculate the resistance in series and parallel circuits?
• Series: Add up the resistance of all the components • Parallel: 1/RT = 1/R1 + 1/R2 + ………..
SP10d - What is key to remember about the size of the total resistance in series and parallel and series circuits?
• S: It is greater than any of the individual resistances • P: It is smaller than all of the individual resistances
SP10e - What does a IV graph for fixed resistor look like and why?
• It is a straight diagonal line showing direct proportion. • This is because resistors are ohmic conductors. • The voltage is directly proportionate to the current.
SP10e - What is an ohmic conductor?
A component in a circuit that follows Ohm’s rule of V=IxR
SP10e - What does the gradient of an IV graph represent?
The inverse of the resistance (1/R)
SP10e - What does a IV graph for diode look like and why?
• 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
SP10e - What does a IV graph for filament lamp look like and why?
• 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
SP10e - Describe what a graph for resistance of a thermistor would look like and why.
• 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.
SP10e - Describe what a graph for resistance of an LDR (Light-dependant resistor) would look like and why.
• 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