Electricity Flashcards
What is the equation for energy transferred?
E = V x Q Energy transferred = Voltage x Charge or E = V x I x t Energy transferred = Voltage x Current x Time
What is the equation for potential difference?
V = W / Q Voltage = Work Done / Charge
What is the unit for charge?
Coulombs
What is the unit for work done?
Joules (J)
What is Ohms Law?
V = I x R
What is the equation for charge?
Q = I x t Charge = Current x Time
What is the rule for CURRENT in a SERIES circuit?
Current is the SAME everywhere in the circuit.
I1 = I2 = I3
What is the rule for VOLTAGE (or P.D.) in a SERIES circuit?
The voltages of all the components ADD UP to the voltage of the battery.
V Battery = V1 + V2 + V3
What is the rule for CURRENT in a PARALLEL circuit?
The current in each branch ADDS UP to form the total current going in and out of the battery.
I Total = I1 + I2 + I3
What is the rule about VOLTAGE (or P.D.) in a PARALLEL circuit?
The voltage of each branch is the SAME as the battery voltage.
V Battery = V1 = V2 = V3
What is the rule about RESISTANCE in a SERIES circuit?
Total resistance is equal to the resistance of all the components ADDED UP.
R T = R1 + R2 + R3
What is the rule about RESISTANCE in a PARALLEL circuit?
1/RT = 1/R1 + 1/R2 + 1/R3
How can you tell if a graph is directly proportional?
The line is straight and goes through the origin.
What does a directly proportional V/I graph tell you about a component?
It is an Ohmic resistor.
What is current?
The flow of charge (electrons).
What is a battery?
Two or more cells connected together.
What does Ohm’s law state?
Current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
What does the gradient of the line in a V/I graph tell you about the component?
The steeper the line, the greater the resistance.
What is an Ohmic resistor and a Non-Ohmic resistor?
Ohmic
• Straight line through origin (V/I graph)
• Resistance does not change with increased current
Non-Ohmic
• Curved line (V/I graph)
• Resistance changes with increased current
Why does resistance increase with current in Non-Ohmic resistors?
Greater current heats up the wire. This causes the ions in the metal to vibrate more, blocking flow more and therefore increasing resistance. The result is a curved graph.
What are some examples of Non-Ohmic and Ohmic resistors?
Ohmic • Fixed Resistor Non-Ohmic • Filament Bulb • Diode
What does the V/I graph look line for a fixed resistor?
Straight line through the origin.
What does the V/I graph look line for a filament bulb?
It curves away from the current axis as current increases.
What does the V/I graph look line for a diode?
Along the voltage axis until a certain current, then sudden spike up.
What does a diode do?
Allows current to flow in one direction. Very high resistance one way, very low the other way.
What does an LDR (Light Dependent Resistor) do?
Resistance increases as light intensity decreases.
What does a thermistor do?
Resistance increases as heat decreases.
What experiment can be used to work out the resistance of a wire/component?
- Circuit with battery, variable resistor, ammeter, component and a voltmeter around it.
- Variable resistor is used to change current.
- At various currents, the potential difference is recorded.
- A V/I graph can be plotted.
- R = V/I can be used to calculate the resistance.
Other Stuff To Revise…
- Different component symbols and functions
* Drawing V/I graphs
