Parallel and Series Circuits Flashcards
What happens when insulating materials are rubbed together?
Electrons are scraped off one and dumped on the other.
When a duster is rubbed on a polythene rod, which way do the electrons move?
From the duster to the rod.
With a Polythene rod, the duster becomes Positive
When a duster is rubbed on an acetate rod, which way do the electrons move?
From the rod to the duster.
What are positive static charges caused by?
Electrons moving away.
What are conductors?
Materials which charges can easily pass through.
How does resistance affect current?
The greater the resistance, the smaller the current.
What is current?
The rate of flow of charge.
What is current measured in?
Amperes (A)
What is the formula that connects charge, time and current?
Charge = Current / Time A = C / s
What is potential difference?
Work done per unit charge.
What is potential difference measured in?
Volts (V)
What is the formula that connects potential difference, charge and work done?
P.D = Work done / Charge V = J / C
Where can ammeters be placed?
Anywhere in series.
Where can voltmeters be placed?
In parallel across the component under test.
What do variable resistors control?
The current flowing through the circuit.
Describe the graph for resistors.
Directly proportional to P.D.
Describe the graph for a filament lamp.
As the temperature of the filament increases, the resistance increases.
Describe the graph for a diode.
Current only flows in one direction, so resistance is very high in the other direction.
Why does resistance increase with temperature?
- Heat energy causes the ions in the conductor to vibrate more
- Harder for charge-carrying conductors to get through
What formula connects potential difference, current and resistance?
P.D = Current x Resistance V = I x R
What is a diode used for?
To regulate the potential difference in circuits.
When do LEDs emit light?
When current flows through in the forward direction.
What is an LDR?
Resistors that depend on light intensity.
When is resistance highest for an LDR?
In darkness.
What is a thermistor?
A temperature dependent resistor.
When is resistance highest for a thermistor?
Cool conditions.
What happens to potential difference in series circuits?
The voltages around the circuit add up to the source voltage.
What happens to current in series circuits?
The same current flows through all parts of the circuit.
What happens to resistance in series circuits?
The total resistance is the sum of all the resistances.
What happens to cell voltages in series circuits?
They add up.
What happens to potential difference in parallel circuits?
The voltage is the same across all components.
What happens to current in parallel circuits?
The total current flowing around the circuit is equal to the total of all the currents through the separate components.
