chapter 13 electrical systems Flashcards
what is electric currents? and how is it measured?
- the rate of flow of electric charge
- it is measured by the amount of electric charge moving per unit time past any point in the circuit
what is the SI unit for current?
- Ampere (A)
- one ampere of current means that one unit of charge flows per second
what current flows from a positive terminal of a battery to a negative terminal of a battery? and what current moves from a negative terminal to a positive terminal?
- conventional current
- electron flow
name the function of these things in a circuit:
- switch
- energy source
- wires
- bulb
- it turns the current on or off
- provides energy for the current to flow in a circuit
- connects the components together and provides a path for the current to flow
- converts electrical energy into light and heat
what is a series circuit?
when the components are joined one after another in a single loop
- electrical current passes through one single path
what is a parallel circuit?
- electric current is divided into branches
- electrical components are connected in each branch
- electric current will pass through all the branches
what is potential difference?
- the p.d of any two points is the amount of energy needed to move one unit of electric charge from one point to another
What is the SI unit of potential difference?
- volts (V)
- one volt of potential difference means that you need one joule of energy is needed to move one unit of electrical charge
what is resistance?
- the resistance of a component is the ratio of potential difference across it to the current flowing through it
- the electrical component resists or hinders the flow of electric charges when it is connected in a circuit
what are variable resistors?
- rheostat
- a resistor whose resistance can be adjusted easily
- when slider is on the left- short resistance
- when sliders is on the right - long resistance
what are the effects of electric current?
- magnetic effect
- chemical effect
- heating effect
- lighting effect
what are the chemical effects of electric current?
extraction of metal ( electrolysis):
- electricity can be used to break down compounds into its elements
eg. aluminum can be extracted from bauxite
electroplating:
-coating objects with metal by immersing the object in a liquid and then passing an electric current through the liquid
what is the magnetic effect of electric current?
electromagnets:
- magnetic effect by making current flow in a coil of wire (solenoid)
- an iron rod can be placed inside which will turn the iron rod into an electromagnet
what is the heating effect of an electric current?
-electrical energy passes through a wire and is converted to heat energy
> heating elements are made of materials with high melting points like
>nichrome, iron, Nickle and chromium
what is the lighting effect of an electric current?
- in a light bulb, the current causes the filament to heat up and therefore glows and gives out light
what is power?
the power of a circuit component is the amount of electrical energy converted to other forms of energy per unit time by the component
What is the SI unit of power?
- watt (W)
- one watt of power means that in one second, one joule of energy is converted to other forms
what does the power rating of an appliance tell us?
- how quickly an electrical appliance converts electrical energy to other forms of energy
what is the unit for power and what is the unit for energy?
power: watt (W)
energy: Joule (J)
What is the formula for energy?
energy = power x time
j or kWh = w x h
What are the three wires in an electrical appliance?
Earth wire: (yellow and green) connected to the ground on earth: it provides a path of low electrical resistance, the large current flows directly into the ground
live wire: (brown)
neutral wire
what is a fuse and what does it do?
- a short thin wire
- it makes use of the heating effect of an electric current to switch off a large current
- a large current causes the shorth thin wire in the fuse to heat up and melt
- a fuse is connected to a live wire
> is rated with the current that will melt the wire in it - if the fuse melts, it has ‘blown’
> needs to replace after an electrical fault
what is a circuit breaker?
- it cuts off electric current but does not need to be replaced
- found in a box called consumer unit
- the main switch turn off or on all electricity in the household
- when the current in one part is too large, usually only the circuit breaker for that part turns off ‘trips’
what are heating elements made of?
- nichrome
an alloy of chronium, nickle and iron
