Flashcards in Electricity Deck (88)
What is electric current?
The flow of electrical charge/electrons. The unit of current is the ampere, A
What is potential difference?
The energy transferred per each coulomb of charge between two points in a circuit. Its unit is the volt, V (pushes charge round)
What is electrical resistance?
The ratio of the P.D. across a component to the current through the component. Its unit is ohm, Ω (measure of how difficult it is for current to flow through a component)
What is the relationship between resistance and current?
The greater the resistance across a component, the smaller the current that flows (for a given potential difference across the component).
What is the size of a current?
The rate of flow of charge
How do you work out the charge flow (size of current)?
Charge flow (coulombs, C) = Current (A) x Time (s)
Q = It
How do you calculate potential difference with current and resistance?
Potential difference (V) = Current (A) x Resistance (Ω)
What does an ammeter do?
-Measures the current (in amps) flowing through wire
-Must be placed in series with whatever you are investigating
What does a voltmeter do?
-Measures the potential difference across a wire (volts)
-Must be placed in parallel around what you are investigating
What effect does resistance have on potential difference?
The higher the resistance, the more potential difference that is required
What are sensing circuits?
Sensing circuits can be used to turn on or increase the power to components depending on the conditions they are in
What is a series circuit?
A circuit in which the different components are connected in a line, end to end between the + and - parts of the power supply. If one component is removed or disconnected, the circuit is broken
Describe the distribution of PD in a series circuit?
The total PD of the supply is shared between the various components. The potential difference round the circuit always adds up to equal the source PD
Describe the distribution of current in a series circuit?
The same current flows through all components
How do you calculate the total resistances of components in a series circuit?
Sum the resistance of each component because adding resistors, shares the total PD
What happens to the current and resistance in a series circuit when a resistor is added?
The PD across the resistors is lower, so the current through each resistor is also lower. Therefore, the total current, as it is the same throughout, is reduced. This means the total resistance of the circuit increases.
What is a parallel circuit?
A circuit in which each component is separately connected to the + and - of the supply. (except for ammeter in series)
What is the distribution of PD like in parallel circuits?
All components get the full source of PD, so the potential difference is the same across all components
How is current shared in a parallel circuit?
The total current flowing around the circuit is equal to the total of all the currents through the separate components. The current splits or rejoins at the different junctions but the total current going into a junction has to equal the total current leaving. Identical components receive the same current
What happens to the total resistance of a parallel circuit when a resistor is added? Why?
The total resistance reduces. Each resistor has the same PD as the source whatever the quantity. Adding another loop with the resistor, means the current has more than one direction to go in, this increases the total current that can flow round the circuit. Using R= V/I, an increase in current means a decrease in the total resistance of the circuit
What causes static electricity?
Frictional forces and therefore the movement of electrons onto or off a material
How is a negative static charge created?
From the movement of electrons onto an object
How is a positive static charge created?
From the movement of electrons off of an object
What do all charges want to do?
Ground (go to earth)
What is sparking?
When an object builds up an electric charge and the potential difference gets large enough (difference between object and 0V Earth), so electrons jump the gap or to earthed conductors.
What does a potential difference of 10,000V mean?
this means that if a coulomb of charge transfers across this potential difference, it will transfer 10,000J of energy
Where are some common examples of static electricity uses?
Inkjet and laser printers, spray painting and carbon capture with charged chimneys and particulates
Where are electric fields created?
Around any electrically charged object
What are the rules and symbolism of electric field lines?
-Flow from positive to negative
-Always at a right angle to the surface
-Closer the lines, stronger the force