Electric Circuits Flashcards
What is the current?
- rate of charge of flow
- how many electrons are flowing per second
- measure in Amps, A
What is potential difference?
- the driving force the ‘pushes’ the electrons round the circuit
- AKA Voltage
- measure in volts, V
What is resistance?
- resists the flow of charge
- measured in ohms, Ω
Equation for current?
Charge flow (coulombs, C) = current (A) x time(s)
Q=It
What are all the circuit symbols
revise on pg 24 in cgp
Formula for potential difference
Potential difference (V) = Current (A) x Resistance (Ω)
V=IR
State the Ohms law equation
V = I x R
State Ohm’s law in words
Voltage is directly proportional to current and resistance
What does the ammeter measure and where should it be placed ?
Current (amps)
Ammeter must always be connected in the series
what does the voltmeter measure and where should it be placed?
Potential difference (V)
Always places parallel, around what your investigating
What is an Ohmic conductor?
a conductor through which current and potential difference are directly proportional, so you get a straight line
Describe the relationship between the current and temperature in a filament lamp
- As the current increases, the temperature of the filament increases, so the resistance increases.
- This means less current can flow per unit pd, so
the graph gets shallower - hence the curve.
as the bulb is left on, it heats up so its resistance increases and less charge can be pushed as current. This makes the line less steep.
Describe how a diode works
Current will only in one direction.
- The diode has extremely high resistance in the reverse direction.
- Once the current passes the threshold voltage it can flow because of the lower resistance.
- Diode behave like an oh in conductor past the threshold voltage.
What shape is a potential difference to current graph for a filament bulb?
S shape
What is a LDR
Light Dependent Resistor- used to detect light levels (dependent on light intensity)
Describe the relationship between light intensity and resistance in an LDR.
as light intensity goes up (bright light), resistance goes down
In darkness, resistance is the highest
L.U.R.D - light intensity . Up. Resistance. Down
What is a thermistor?
resistor whose resistance is dependent on temperature
Describe the relationship between temperature and resistance in a thermistor.
as temperature goes up, resistance goes down
T.U.R.D - Temperaturen . Up. Resistance. Down
Describe the rule for current in series.
the same current passes through each component (same current value )
I1 = I2 = …
Describe the rule for voltage in series.
the total voltage is shared between the components (shared equally)
Vt = V1+V2+…
Describe the rule for resistance in series.
Total resistance is shared (doesn’t have to be equal)
Rt = R1 + R2 + …..
What are the cons of a series circuit?
If one component is disconnected or broken, the circuit is broken and they all stop.
Pros of parallel circuits
- each component is connected separately to the +ve and -ve.
- if one is removed or disconnected it will hardly effect the others at all.
Describe the rule for current in parallel .
current is shared
It = I1 + I2 + ….
