2.1 Current, potential difference, resistance Flashcards
2.1.1 Standard circuit components
What are the standard circuit components and their function?
- Switch - turns a circuit on (closed) and off (open)
- Filament lamp - can indicate the presence of current in a circuit
- Fuse - melts to break the circuit if the current is too high
- Diode - ensures the current travels in one direction only
- Voltmeter - measures the potential difference (voltage) in a circuit
- Ammeter - measures the current in a circuit
- Resistor - restricts the flow of electric current
- Variable resistor - restricts the flow of electric current to varying degrees
- LED - indicates the presence of current
- LDR - restricts the flow of electric current depending on light intensity
- Thermistor - restricts the flow of electric current depending on temperature
- Cell - converts chemical energy into electrical energy to provide the current
- Battery - a collection of cells
- Lamp - indicates the presence of current
2.1.2 Electrical charge and current
Electric current definition and formula
Electric current is a flow of electrical charge
Charge flow = current x time
Q = I t
Charge flow - coulombs (C)
current - amperes/amps (A)
time - seconds (s)
2.1.3 Current, resistance, potential difference
Relationship between current, resistance, voltage
- higher resistance, the smaller the current (for a fixed voltage amount)
- higher current = higher voltage
2.1.3 Current, resistance, potential difference
current, resistance, voltage
relationships, and definition
- higher resistance, the smaller the current (for a given voltage amount)
Current: the flow of electrical charge.
Voltage: the push of electrical charge.
Resistance: slows down the flow of electricity.
2.1.3 Current, resistance, potential difference
Formula linking current, resistance, voltage
Voltage = current x voltage
V = I R
potential difference - volts, V
current - amperes/amps , A
resistance - ohms, Ω
2.1.4 Resistors
What happens to the resistance in an ohmic conductor
graph
- the resistance remains constant as the current changes
- the current through an ohmic conductor (at a constant temp) is directly proportional to the potential difference across the resistor.
Graph:
* x-axis - potential difference
* y-axis - current
* straight, diagonal line through the origin
2.1.4 Resistors
What happens to the resistance in a filament lamp?
graph
- filament lamp is a non-ohmic conductor (not resistor)
- temperature increases, so resistance increases
- temp increasing, means atoms vibrate more, more collisions so its harder for electrons to flow, so it increases the resistance
Graph:
* x-axis - potential difference
* y-axis - current
* ƒ shape, straight through the origin. ends of the line is curves
2.1.4 Resistors
What happens to the resistance in a diode?
graph
- current through diode flows in one direction only
- the diode has a very high resistance in the reverse (opposite/wrong) direction
graph:
* x-axis - potential difference
* y-axis - current
* flat, horizontal line on x axis. halfway of the right x-axis line, current increases with potential difference
* no current until potential difference increases
2.1.4 Resistors
What happens to the resistance in a thermistor
graph
- temperature increases, making resistance decrease
- when its hot, more electrons collide energetically, meaning that more electrons are moved (larger current), whilst the voltage stays the same.
- R=V/I - when current increases, resistance decreases.
- temperature increases, current increase, resistance decreases.
Graph:
* x-axis: temperature
* y-axis: resistance
* curve, begins at the top of resistance, falls down to end of temperature. low temp/high resistance; high temp/low resistance
2.1.4 Resistors
What happens to resistance in an LDR?
- resistance decreases, when light intensity increases
Graph:
* x-axis: temperature
* y-axis: resistance
* curve, begins at the top of resistance, falls down to end of light intensity. low light/high resistance; high light/low resistance
