Current electricity Flashcards
Insulating
Reducing energy transfer by conduction
Electron
A tiny particle with a negative charge
Attract
To cause to move nearer
Repel
To cause to move apart
Series
Components connected in a circuit so that the same current passes through them
Potential difference
The amount of work done by each coulomb of charge that passes through a component
Parallel
Components connected in a circuit so that the potential difference is the same across each one
Volt (V)
The unit of potential difference
V=W/Q=E/Q
potential difference (V) = work done (J) ÷ charge (C) = energy transferred (J) ÷ charge (C)
Resistance
The opposition to current flow, measured in ohms, Ω
R=V/I
resistance (Ω) = potential difference (V) ÷ current (A)
Ohmic conductor
A conductor that has a constant resistance, and therefore obeys Ohm’s law
I=Q/t
current (A) = charge (C) ÷ time
Filament bulb
An electrical device designed to produce light
Diode
An electrical device that allows current through in one direction only
Light-dependent resistor (LDR)
A device with a resistance that varies with the amount of light falling on it
Thermistor
A device with a resistance that varies with temperature
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 when objects become charged
What happens when charges are brought together?
Like charges repel; unlike charges attract
Why are electric charges represented by circuit diagrams?
Every component has its own agreed symbol. A circuit diagram shows how components are connected together
What is the difference between a battery and a cell?
A battery consists of two or more cells connected together
What determines the size of an electric current?
The size of an electric current is the rate of flow of charge
What do we mean by potential difference?
The potential difference is the amount of work done by each coulomb of charge that passes through a component
What is Ohm’s law?
Ohm’s law states that 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 pd across it
What happens to the resistance of a filament bulb as its temperature increases?
The resistance increases with the increase of the filament temperature
Why does the resistance of a filament bulb increase as its temperature increases?
The ions in the metal filament vibrate more as the temperature, so they resist the passage of electrons through the filament more
How does the current through a diode depend on the potential difference across it?
In the “forward” direction a diode’s 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 the temperature increases
What happens to the resistance of an LDR as the light level increases?
The resistance decreases if the light intensity on it increases
What can we say about the current and potential difference for components in a series circuit?
For components in series, the current is the same in each component, and adding the potential differences gives the total potential difference
How can we find the total resistance of resistors in series?
Adding the resistances gives the total resistance of resistors in series
What can we say about the potential difference of several cells in series?
For cells in series, acting in the same direction, the total potential difference is the sum of their individual potential differences
What can we say about the currents in the components of a parallel circuit?
For components in parallel, the total current is the sum of the currents through the separate components, and the bigger the resistance of a component, the smaller its current is
What can we say about the potential differences across the components in a parallel circuit?
In a parallel circuit the potential difference is the same across each component
