Current Electricity Flashcards
What happens when insulating materials are rubbed together?
Certain insulating materials become charged when rubbed together.
What is transferred when objects become charged?
Electrons are transferred:
- insulating materials that become positively charged when rubbed lose electrons
- insulating materials that become negatively charged when rubbed gain electrons
What happens when charges are brought together?
Like charges repel.
Unlike charges attract.
What is a cell?
It is necessary to push electrons around a complete circuit.
What is a battery?
It consists of two or more cells.
What is a switch?
It enables the current in a circuit to be be switched on/off.
What is an indicator?
- emits light as a signal when a current passes through it
* light source
What is a diode?
It allows current through one directions only.
What is a light-emitting diode (LED)?
It emits light when a current passes through it.
What is an ammeter?
It is used to measure electric current.
What is a fixed resistor?
It limits the current in a circuit.
What is a variable resistor?
It allows the current to be varied.
What is a fuse?
It melts and therefore breaks the circuit if the current through it it greater than a certain amount.
What is a heater?
It transfers electrical energy to heat the surroundings.
What is a voltmeter?
It is used to measure potential difference.
What is the size of an electric current?
The rate of flow of electric charge.
What is electric current?
The flow of charge.
How can we calculate the size of an electric current?
Current (A) = charge flow (C) / time taken (s)
What is potential difference?
A measure of the work done or energy transferred to the lamp that passes through it.
How do we measure the potential difference?
Potential difference (V) = work done (J) / charge (C)
What is resistance?
Resistance (ohms) =potential difference (V) / current (A)
What is Ohm’s law?
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
What happens if you reverse the current in a resistor?
Reversing the current through a component reverses the potential difference across it.
Why is a wire an panic conductor?
It’s resistance is constant.
What happens to the resistance of a filament bulb as its temperature increases?
The resistance increases with increases of the filament temperature.
How does the current through a diode depend on on the potential difference across it?
In the ‘forward’ direction, the resistance is low.
In the ‘reverse’ direction, the resistance is high.
What happens to the resistance of a thermistor as its temperature increases?
The resistance decreases if its temperature increases.
What happens to the resistance of a light-dependent resistor (LDR) as the light level increases?
The resistance decreases if the light intensity on it increases.
Where are thermistors and LDRs used?
In sensor circuits.
What happens to the current in series circuits?
The same current passes through components in series with each other.
What happens to the potential difference of the voltage supply in series circuits?
The total potential difference of the voltage supply in a series circuit is shared between the components.
What happens to the potential difference of cells in series circuits?
The total potential difference of cells in series is the sum of the potential difference of each cell.
How can we find the total resistance of resistors in series?
The total resistance of components in series is equal to the sum of the resistance of each component.
How can we calculate the current though a resistor in a parallel circuit?
Current (A) = potential difference (V) / resistance (ohms)
What can we say about the currents in the components in a parallel circuit?
- the total current is the sum of the currents through the separate components
- the bigger the resistance of a component, the smaller its current is.
What can we say about the potential difference across the components in a parallel circuit?
The potential difference is the same across each component.
