Electricity Flashcards
Definition of electrical current as the electric charge transferred per unit time
When charge carriers are given charge (coulombs) from the supply and go round a circuit from the positive end of the supply to the negative. The charge carriers are full of positive charge and therefore repel away from the positive end of the supply and attract to the negative end of the supply which makes the current of energy going round the circuit constantly. The charge carriers repel off each other which makes them go further round the circuit.
What is the formula that links charge, current and time in a circuit?
Q = IT
Q - Charge (coulombs)
I - Current (Apms,A)
T - Time (seconds)
What is alternating current?
The charge carriers go “to and fro”. They keep alternating direction. It has a peak value which is the highest amount of current it has.
What is direct current?
The charge carriers all flow in the same direction and the amount of current does not vary. It also has a declared value.
Identification of a source (as a.c. or d.c.) based on oscilloscope trace or image from data logging software.
UK Mains is a.c and has a frequency of 50Hz
What force do charged particles experience in an electric field?
Like charges repel.
Opposite charges attract.
Negative electric charges(electrons) are free to move.
What path will a charged particle follow when between two oppositely charged parallel plates?
If a positive charged particle is placed anywhere between the two plates it will accelerate towards the negative plate and likewise if the particle is negative.
What path will a charged particle follow when near a single point charge?
Depending on if it is positive or negative the particle will either attract or repel.
What path will a charged particle follow when between
two oppositely charged points?
If a positive charged particle is placed anywhere between the two points it will accelerate towards the negative side and the reverse if the particle is negative.
What path will a charged particle follow when between two like charged points?
If the particle is positive and the two points are negative and the positive particle is placed in the middle of the two points then the particle will stay in the middle, but if the particle is placed further to one side of the points then the particle will attract towards the point that is closest to it. This is the same if the particle is negative and the two points are positive.
If the particle is positive and the two points are positive and the positive particle is placed in the middle of the two points then the particle will stay in the middle, but if the particle is placed further to one side of the points then the particle will be pushed into the middle of the two points. This is the same if the particle is negative and the two points are negative.
What is the calculation of the gradient of the line of best fit on a V-I graph to determine resistance?
V/I = R
V - Potential Difference (voltage)
I - Current (Amps)
R - Resistance (Ohms)
What is the appropriate relationships to solve problems involving potential difference (voltage), current and resistance(Ohms Law)?
V = IR
V - Potential Difference (voltage)
I - Current (Amps)
R - Resistance (Ohms)
What is the relationship between resistance and temperature in a conductor?
The higher the temperature the higher the resistance. If the temperature drops then there is less resistance. If the temperature increases then there is more resistance.
Description of an experiment to verify Ohm’s law.
- Set up a circuit with a variable d.c supply connected to an ammeter and a resistor with a voltmeter connected to it.
- Vary the d.c power supply to change the current, using the ammeter to note the value.
- Measure the p.d using the voltmeter.
- Using the results, plot a graph of p.d against current.
- The gradient of the line of best fir is constant showing the direct proportionally between V and I. The gradient of the line in the graph matches the value of the resistor. The experiment shows V/I = R.
Measurement of current, potential difference (voltage) and resistance, using appropriate meters in a series circuit.
In a series circuit current is the same at all points:
I1 = I2 = I3 = I4…
In a series circuit, the potential difference (voltage) across each component adds up to the supply potential difference:
Vs = V1 + V2 + V3…
In a series circuit this is the formula to find the total resistance:
RT = R1 + R2 +R3…
Measurement of current, potential difference (voltage) and resistance, using appropriate meters in a parallel circuit.
In a parallel circuit the potential difference (voltage) is the same at all points:
V1 = V2 = V3 = V4…
In a parallel circuit, the total current adds up to the sum of the current, the p.d across each of the branches is equal to the supply
Is = I1 + I2 + I3…
In a parallel circuit this is the formula to find the total resistance:
/1RT = 1/R1 + 1/R2 + 1/R3…
What is the circuit symbol, function and
an example application for a cell?
Circuit symbol = (draw on piece of paper)
Function = Provides voltage
Example Application = Combining into a battery
What is the circuit symbol, function and application for a battery?
Circuit symbol = (draw on piece of paper)
Function = Provides voltage
Example Application = Powering circuits
What is the circuit symbol, function and application for a lamp?
Circuit symbol = (draw on piece of paper)
Function = Producing light
Example Application = Lightning
What is the circuit symbol, function and application for a switch?
Circuit symbol = (draw on piece of paper)
Function = Controlling current (on/off)
Example Application = Various
What is the circuit symbol, function and application for a resistor?
Circuit symbol = (draw on piece of paper)
Function = Controlling resistance (fixed)
Example Application = Potential dividers
What is the circuit symbol, function and application for a variable resistor?
Circuit symbol = (draw on piece of paper)
Function = Controlling resistance
Example Application = Potential dividers
What is the circuit symbol, function and application for a voltmeter?
Circuit symbol = (draw on piece of paper)
Function = Measuring potential difference
Example Application = Fault finding
What is the circuit symbol, function and application for a ammeter?
Circuit symbol = (draw on piece of paper)
Function = Measuring current
Example Application = Electrical safety
