Topic 2 - Electricity Flashcards
What is current?
The flow of electric charge
What is potential differece?
The driving force that pushes current round a circuit
What is resistance?
Anything that slows the flow of current down
What is the rule for current in a series circuit?
Current is the same everywhere
What does current need to flow?
Potential difference
What does the strength of the current depend on?
- The amount of potential difference
2. The amount of resistance
What is an ohmic conductor?
Conductors that have a constant resistance at a constant temperature, therefore, the current flowing across an ohmic conductor is directly proportional to the potential difference
Why does the resistance of a filament lamp change?
Some energy is transferred to the thermal energy store in the lamp which then increases the temperature which in turn increases the resistance
Why is resistance in a diode so intersting?
It depends on the direction of the current, one way there is very little resistance but if the current is reversed then the resistance is very high
What does the I-V graph look like for an ohmic conductor?
y = x
What does the I-V graph look like for a filament lamp?
y = x**3
What does the I-V graph look like for a diode?
y = 2**x
What does an LDR do?
The resistance of an LDR changes based on the light intensity, as the light intensity increases the resistance decreases and as it decreases the resistance increases
What does a thermistor do?
The resistance changes based on the temperature, as the temperature increases the resistance decreases and as the temperature decrease the resistance increases
What does a sensing circuit do?
A sensing circuit will contain a component such as an LDR or thermistor so that when an external condition changes the conditions within the circuit will change as well, they will increase or decrease power based on the conditions
How would you connect a component to an LDR if you want the LDR to affect that component?
You would connect the component in parallel across the LDR
What component is connected in parallel in a series circuit?
A voltmeter
What is the rule for potential difference in a series circuit?
- Cell potential difference adds up in a series circuit provided all the cells are connected in the same way
- The total cell potential difference is shared amongst all components in the circuit
What is the rule for current in a series circuit?
Current is the same everywhere
What is the rule for resistance in a series circuit?
Resistance adds up
What is the rule for potential difference in a parallel circuit?
Potential difference is the same across all components
What is the rule for current in a parallel circuit>
Current is shared between branches (the amount of current on each branch is dependent on the components on that branch)
What happens if you add a resistor in a parallel circuit and why?
Adding a resistor reduces the total resistance because the resistance in a parallel circuit is always equal to the resistance of the lowest resistor
What is the difference between AC and DC?
AC is mains supply where as DC is battery supply.
Direct Current always flows in the same direction where as Alternating Current changes direction.
AC is caused by an alternating potential difference where as DC is caused by a constant potential difference.
