Studied by 3 people
define electromotive force (emf)
the energy per unit charge converted into electrical energy
define potential difference
the work done by an electron per unit charge to move from one point in the circuit to another
conventional current flow?
positive to negative
define current
the rate of flow of charge
electron flow?
negative to positive
what is a diode?
a component that only allows current to flow through in one direction.
define internal resistance
the unavoidable resistance any power source will have that makes it harder for current to flow through the source. it causes energy to be dissipated in the source.
kirchhoffs first law ?
the total current entering a junction is equal to the total current leaving it
kirchoffs second law?
the sum of EMF in any loop of the circuit is equal to the sum of potential differences of each component
define power and its units
the rate of energy transfer (watts)
define resistance
a measure of how difficult it is for current to flow in a circuit or component. opposition to flow of charge
define resistivity
a measure of how difficult is it for charge to travel through a specific material.
what is a semiconductor
materials that change their resistance depending on external conditions
what is an ohmic conductor
the current flowing through is directly proportional to the potential difference between each end of the conductor (at constant temperature)
ohms law?
electric current is directly proportional to potential difference and inversely proportional to resistance (at constant temperature)
how is current split in a parallel circuit?
the current is split between the branches
how is current split in a series circuit?
current is the same across all components
how is potential difference split in a parallel circuit
potential difference over each loop is the same
how is potential difference split in a series circuit?
potential difference is split between components depending on their resistance.
what is terminal potential difference?
the actual potential difference across the terminals of a power source. it is the EMF minus the lost volts due to the sources internal resistance
what is a voltmeter?
a device used to measure the potential difference between two points on a circuit, ideally it has infinite resistance so no current can pass through
what is a superconductor?
materials with zero resistivity at below a critical temperature
2 examples of semiconductors
thermistors and LDRs
describe the IV characteristic of a filament bulb
as current increases, temperature increases, causing the metal ions to vibrate with more kinetic energy, making it harder for charge carries to pass through so resistance increases.
why is terminal potential difference never the same as the EMF value?
energy is dissipates within the source due to the cells internal resistance
What is electric field strength?
The force per unit charge experienced by a small positive test charge placed in the field.
Define capacitance.
The ability of a component to store charge per unit voltage, measured in farads.
What is a capacitor?
A device used to store electrical energy in an electric field.
What does a capacitance value of 1 farad mean?
A capacitor stores one coulomb of charge at one volt.
What is the formula for energy stored in a capacitor?
E = 1/2 CV², where E is energy, C is capacitance, and V is voltage.
What is the purpose of a fuse in a circuit?
To protect the circuit by breaking the connection when current exceeds a safe level.
What factors affect resistance in a conductor?
Length, cross-sectional area, temperature, and resistivity of the material.
What is a series circuit?
A circuit where components are connected end-to-end, so the same current flows through each component.
What is a parallel circuit?
A circuit where components are connected across common points, providing multiple paths for current.
What is a variable resistor?
A resistor whose resistance can be adjusted to vary the current or voltage in a circuit.
What is electrostatic induction?
The redistribution of electric charge in an object due to the influence of nearby charges.
What is a potentiometer?
An instrument used to measure the potential difference by comparing it to a known reference voltage.
What is a thermistor?
A temperature-sensitive resistor whose resistance varies significantly with temperature.
What is an ammeter?
A device used to measure the current flowing through a circuit, ideally has zero resistance.
