Energy and Voltage in circuits Flashcards
What is parallel circuits best for?
For domestic lighting (turning a light of in a room), household electrics
What is series circuits best for?
Fairy lights
How would you calculate current in a series circuit?
Current = voltage/resistance
I = V/R
Unit for current
Ampere (A)
Unit for electrical charge
Coulomb (C)
Unit for energy
Joules (J)
Unit for resistance
Ohms (Ω)
Unit for time
Seconds (s)
Unit for voltage
Volts (V)
Unit of power
Watt (W)
What happens if a circuit is broken or a component is removed in a series circuit?
It will all stop working
Does the current change in a series circuit?
No it stays the same everywhere
What does the size of current depend on in a series circuit?
The size of current depends on the potential difference (v)
How is the potential difference (v) shared in a series circuit?
It’s shared between components and the p.d. depends on the resistance of the component
How to calculate total resistance? (Rtotal)
Total resistance = resistance1 + resistance 2…
Rtotal = R1 +R2…
What does the total resistance in a circuit depend on?
The number and type of components.
How is the current shared in parallel circuits?
The current is shared between branches
How to calculate total current?
Add up the separate currents of each component.
ITotal = I1 +I2
What happens if you remove or disconnect a component in a parallel circuit?
It will hardly effect the other components
How is the voltage shared in a parallel circuit?
The voltage is the same throughout
How does the current change in a branch depending on the components?
The current depends on the resistance, high resistance of component = lower current flow
How does the total resistance change if a second resistor is added in a parallel?
The total resistance will decrease. It will be less than the smaller resistor
What does the current equal going in a branch and going out the same branch?
They will equal the same as current is conserved.
How to calculate charge (Q)?
Charge = Current x Time
Q = I X t
What is potential difference (voltage)?
Is energy per unit charge dissipated across an external component
What is EMF?
Electric Motor Force - energy per unit charge supplied by the source
How to calculate energy transferred using charge and voltage?
Energy transferred = Charge x Voltage
E = Q x V
How to calculate energy transferred using charge, current and resistance?
Energy transferred = charge x current x resistance
E = Q x I x R
How does current and voltage vary in wires?
Current is proportional to voltage (at a constant temperature). Straight line
How does current and voltage vary in different resistors?
Current is proportional to voltage (at a constant temperature). Different resistors have different resistances so it will have different slopes. Straight line
How to calculate the gradient of a resistor (axis’s current and voltage)?
The gradiant = 1/resistance
How does current and voltage vary in metal filament lamps?
Voltage increases as current does, increased current means increased temperature of filament. This causes the resistance of the filament to increase. This causes a curve
How does current and voltage vary in diodes?
Current only flows in one direction (positive). Vt is 0.6v
What is Vt?
Threshold voltage - the voltage at which the current flows in a diode.
How can you tell if the current is running in a circuit using components?
An LED or lamp can indicate the presence of current
How would you get the graphs for wire, metal filament lamp, diode and resistors?
You apply this to a standard test circuit (using a variable resistor, your component, an Ammeter and voltmeter)
What is an LDR and what does it look like on a graph?
Light-depending-resistor - In a bright light it has a low resistance and in dim light it has a high resistance. Has a curved line
What are LDR’s used for?
Useful for night lights
What is a thermistor and what does it look like on a graph?
When hot resistance is low, when cold resistance is high.
What are thermistors used in?
Useful in thermostats
What is current?
It’s the rate of flow of charge
What is the electrical current in solid metal conductors?
It’s the flow of negatively charged electrons
What is a volt (using joule and coulomb)?
It’s a joule per coulomb
