P4: Electric Circuits Flashcards
What is an electric current?
The rate of flow of electrons in a circuit
What happens when the electrons from the current pass through the lamp?
Electrons carry energy and pass it to the components of the circuit, where the electrical energy is transferred to light energy and thermal energy
What is the conventional current?
Many years go, scientists thought the electric current flowed from the positive end of the cell to the negative, this is still represented on a circuit diagram, called the conventional current
What is a series circuit?
The current can only flow in one path along the circuit
What is the measure of current?
Amps, using an ammeter
What is the current like in a series circuit?
The same all around
I1=I2=I3
What is a parallel circuit?
A circuit which contains ‘branched’ wires
What is the current like in a parallel circuit?
Current in the branches = total current leaving the cell
What is potential difference/ voltage?
Voltage of 1 tells us that 1 joule of energy is transferred for each coulomb of charge that is moving through the circuit
The pressure from an electrical circuit’s power source that pushes electrons (current) through a circuit
How is voltage measured?
Using a voltmeter
What is the voltage like in a parallel circuit?
Same throughout
V1=V2=V3
Why would two lamps be dimmer when attached in series?
Total energy carried by the current is shared between the two lamps
What is the voltage like in a series circuit?
Total potential difference across the circuit is equal to the potential difference supplied by the cell
What is a battery?
More then one cell joined together in the same direction
What is the potential difference across a battery?
The sum of potential difference across all its cells
What is electrical charge?
The size of the electric current is the rate of flow of electrical charge
Current of 1 amp = 1 coulomb of charge per second
What is the formula for charge flow?
Q = It
Charge flow (C) = current * time (s)
What is the formula for energy transferred?
E = QV
Energy transferred (J) = Charge flow (C) * Voltage (V)
Describe current flow through a wire
An electric current is a flow of electrons through a conductor such as a metal wire. As they move, electrons collide with atoms in the metal , electrical energy is transferred into other forms
What is resistance?
The potential difference required to drive a current through a component
What is the formula for resistance?
V = IR
Voltage = Current * Resistance
(V) (A) (Ω)
What is a resistor?
A circuit component that increases the resistance
What is an ohmic conductor?
A resistor whose current is directly proportional to its voltage, provided all physical conditions remain constant
What happens to the filament in a filament lamb as an electric current passes through it?
It gets hotter (causing it to glow)
What is the graph like for a filament bulb and why is this?
Almost directly proportional, with curved ends.
As the current increases, so does the temperature. resulting in a higher resistance
What is a diode?
A component which only lets current flow in one direction, as it has very high resistance on the other end
What is the graph like for a diode?
No current passes in the reverse direction
Forward direction, current increases as p.d. increases
What are LEDs?
A diode which lets out light when a current flows through
What is resistance like in a series circuit?
Resistors in series add together e.g. R1 = 100Ω + R2 = 50Ω = R3 = 150Ω
What is resistance like in a parallel circuit?
Total resistance is less than the smallest resistance in the circuit. This is because there are more than 1 pathways for a current to take, meaning more current will flow through the resistors
1/R1 + 1/R2 = 1/R3
How does LDR resistance change with light?
Light - Low resistance
Dim - High resistance
How does thermistor resistance change with temperature?
