2.1 - 2.1.3 - Current, Potential difference and resistance Flashcards
What is electrical current?
Electric current is defined as the rate of flow charge
In other words, the size of an electric current is the amount of charge passing through a component per second
How does electrical current flow?
Current flows from the positive terminal to the negative terminal of a cell
How are the wires in an electrical circut designed?
The wires in an electrical circut are made of metal because metal is a good conductor of electricity.
In the wires, the current is a flow of negatively charged electrons
What is the equation for calculating electrical charge?
Charge = Current / Time
Q=IT
How is current measured?
Current is measured using an ammeter
Ammeters should always be connected in series with the part of the circuit you wish to measure the current through
Ammeters measure the amount of charge passing through them per unit time, so the ammeter has to be in series so that all the charge flows through it
What does an ammeter look like?
How are the terminals of a cell arranged?
The terminals of a cell make one end of the circuit positive and the other negative
This sets up a potential difference across the circuit
What is voltage?
The amount of energy transferred per unit of charge passing through the terminals
This means that one volt (the unit of potential difference) is equivalent to one joule (the unit of energy) per coulomb (the unit of charge):
What is the eq for voltage?
Potential difference (voltage) = energy transferred/ charge moved
E=QV
How is voltage measured?
Potential difference is measured using a voltmeter, which can be either
Digital (with an electronic read out)
Analogue (with a needle and scale)
Voltmeters are connected in parallel with the component being tested
The potential difference is the difference in electrical potential between two points, therefore the voltmeter has to be connected to two points in the circuit
What does a volt meter look like?
What is resistance?
Resistance is defined as the opposition to current:
The higher the resistance of a circuit, the lower the current
This means that good conductors have a low resistance and insulators have a high resistance
How can the resistance of a circut be affected?
The resistance of a circuit can be increased by adding resistors (or variable resistors) to it
Every electrical component has a resistance, even wires
What is the relationship between Resistance and Current?
The greater the resistance R of the component, the lower the current I for a given potential difference V across the component
The lower the resistance R of the component, the greater the current I for a given potential difference V across the component
What is the eq for calculating the voltage in a circut?
Voltage = Current/ Resistance
