Chapter 4 Electric Circuits Flashcards
(24 cards)
What is the equation for charge?
Q= I x t
What is a battery?
Consists of 2 or more cells connected together
What is the flow rate of charge?
The size of an electric current
What does the diode do?
only allows current through one way
What does an ammeter do ?
measures current and connected in series
What does a voltmeter do?
measures potential difference and connected in parallel
What is the unit of resistance?
ohms
Electric current
Flow of charge. Electric charge Measured in coulombs and electric current in amps
What determines the size of a electric current?
The rate of flow of electric charge. The bigger the number of electrons that pass through a component each second the bigger the current passing through it.
Potential difference across a circuit
V= E/Q
What is Ohms law?
That the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor. Reversing the potential difference across a resistor reverses the current through it.
What is a wire and why?
An ohmic conductor, it’s resistance stays constant as the current changes
Resistance in a graph
The gradient of a graph depends on the resistance. The greater the resistance the less steep the line
Thermistor resistance
Decreases if temp increases
LDR resistance
Decrease if light intensity increases
Filament light resistance
Increases if temp increases
Diode resistance
Forward resistance is low; reverse resistance is high
Series circuit rules
Same current passes through each component. Total potential difference of the power supply is shared between the components. adding their resistance gives the total resistance
What does adding more resistors in series do?
Increase the total resistance because the current is reduced and total potential difference is the same
Rules in a parallel circuit
Total current is a sum of the current through all the branches.
The potential differences across each component is the same.
The bigger the resistance of a component the smaller the current through will pass through it.
Rules for resistance in parallel
Total resistance is smaller than the resistor with the least resistance.
1/rt =1/r1 + 1/r2 …
Current in parallel
Is split between branches
Which way does a circuit flow?
Direct current flows from positive to negative. Electrons are negative
