Recall Facts-circuits 1-30 Flashcards
What is current?
It is the rate of flow of electric charge
Why are metals good conductors?
Because they have free moving electrons
What is the unit for current?
Amps
When a voltage is applied, what end do the electrons move to?
It goes from negative to positive
What is the main difference between conductors and insulators?
Insulated have less free electrons
What is potential difference?
It is another word for voltage. The difference in work done by or on a charge between two points in the circuit.
How is an ammeter connected in a circuit
In series (within the loop)
How is a voltmeter connected in a circuit?
Parallel to the component being measured
How can they be potential difference, but not a current
Incomplete circuit
What is resistance
Opposing the flow of charge (current)
What causes resistance in a wire
Resistance is caused by the electrons colliding with positive metal ions of the wire
State factors that affect the resistance of a wire
Length of wire
Temperature
Thickness of wire
Material of wire
What is the job of a variable resistor?
Alter the resistance of the circuit and therefore current and potential difference across different components
What is the relationship between potential difference and current for fixed resistance
Has the potential difference increases the current also increases
What is the relationship between resistance and current for fix potential difference
As the resistance increases the current decreases
What is the equation linking charge flow current and time?
Charge flow (c)=current (A) x time (S)
Q=I x T
What is the equation for resistance?
Resistance (ohms)=Voltage (V) / Current (A)
State ohms law
Potential difference is directly proportional to the current for a fixed resistor resistor at constant temperature
What is meant by directly proportional?
This is a Y=MX graph (straight line through origin) or when one factor doubles, the other factor also doubles
Describe the difference between linear and non linear graph
Linear graph-straight line
Non linear graph- not a straight or curves
Which of the I-V geaphs are linear
Fixed resistor, resistor at constant temperature
Which of the I-V grapgs are non linear
Filament lamp (bulb) and diode
Explain the shape of the fixed resistor line
Resistance is constant so straight line and follows ohms law
Explain the shape of the filament lamp graph
As potential difference and current increases bulb get hotter and this increases resistance
Explain the shape of the diode graph
Very high resistance in reverse direction for no current very low resistance and forward directions for rapid increase in current
What is power?
How is the rate of energy transfer or how much energy is transferred in one second or power equals energy divided by time
What is power measured in?
Watts
What are the equation for power?
Power (W)=(Current) squares (A) x Resistance (ohms)
p=I squared x R
Power (W) = Potential difference (V) x Current (A)
P=V x I
Energy (J)= Power (W) x time (S)
E=Pxt
