Circuit symbols Instead of drawing intricate diagrams of electrical components we use circuit symbols to simplify how circuits are set up. You will need to learn these, how to draw them, and how to identify them. Filament lamp
Use a textbook or other resource to fill in the table below: Resistor Motor M Switch Fuse Circuit symbol Component
Use a textbook or other resource to fill in the table below: Battery Ammeter A V Voltmeter Cell Circuit symbol Component
Breaks in circuits Set up the circuit shown…. … does the bulb light? Why does the bulb not light? There is a break in the circuit. For electricity to flow in a circuit it must be able to flow from one terminal of the cell or battery to the other terminal. NO
Letting electricity pass Do all materials let electricity pass? Which materials will and which materials will not? Set up the circuit shown and place different materials in the gap in the circuit. Record which materials let electricity through (the bulb lights if electricity flows). What do we call a material that lets electricity flow through it? CONDUCTOR What do we call a material that does not let electricity flow through it? INSULATOR
Which of these bulbs will light? Build the circuits! A. B. C. x x Electricity will always take the easiest path. It is easier to flow through a wire than through the bulb. So in circuits B and C the electricity does not pass through the bulb. The cell or battery still loses energy because , electricity is still flowing. This type of circuit is known as a SHORT CIRCUIT.
Electron flow Electricity in wires is a flow of electrons along the wire. What do we call this flow of electrons? Electrical current
When we talk about current flowing we say that current flows out of the positive terminal of the cell and back into the negative terminal. Current Flow Conventional Current What do we call this flow?
However, the electrons flow from the negative side of the battery to the positive side. These are the particles which are actually moving through the conductor. Electron Flow
When electrons were discovered, physicists worked out what was really happening. Negatively charged electrons are repelled out of the negative terminal of the cell. They then travel round the circuit and are attracted back to the positive terminal. Conventional current and Electron flow Conventional current electrons Conventional current What charge do electrons have? Negative What do two negative charges do if placed near to each other? They will repel each other. What will a positive and a negative charge do to each other? They will attract each other.
In an electric c____, current is the flow of e_______. The bigger the current, the m___ electrons are flowing around the circuit. The w___ carry the electrons from one terminal around the circuit to the other t______. Current lamps ircuit lectrons ore ires erminal
Set up the two circuits shown: In which circuit are the bulbs the brightest? In circuit A the bulbs are the brightest. What happens if you unscrew one bulb in Circuit A? The other bulb stays lit. What happens if you unscrew a bulb in circuit B? The other bulb goes out. What do we call circuit A? Parallel Circuit What do we call circuit B? Series Circuit BRIGHTER DIMMER A. B.
Measuring current I Set up the circuit shown below…… … and then record the current using an ammeter in the places shown below. What do you notice about the readings? The current is the same for each ammeter. In a series circuit the current is the same wherever you measure it. When measuring current ammeters are always placed in series . A A A
Measuring current II Set up the circuit shown below…… … then record the current at the locations shown. What do you notice about the readings? For a parallel circuit, the current that leaves the cell or battery is the same as the current that returns to the cell or battery. The current does not get used up by a circuit, just the energy the electrons are carrying. A 1 = A 4 The sum of the currents in the branches of a parallel circuit is the equal to the current that leaves the cell or battery. A 1 = A 2 + A 3 =A 4 0.8 0.8 0.4 0.4 A 1 A 2 A 3 A 4 A 4 A 3 A 2 A 1 Current (A) Ammeter
The v _____ is a measure of how big a push the e_______ are given as they leave the cell or b_____. The bigger the voltage, the bigger the p___. The cell, battery or p____ s_____ produces the voltage. Voltage lamps oltage lectrons attery ush ower upply
Measuring voltage I V 2 V 3 V 1 Set up the apparatus as shown…… … then record the voltages at the locations shown. What do you notice about the readings? For a series circuit, the sum of the voltages for each component is equal to the voltage across the cell or battery. V 1 = V 2 + V 3 NB Voltmeters are connected in parallel 1.5 0.75 0.75 V 3 V 2 V 1 Voltage (V) Voltmeter
Measuring voltage II V 1 V 2 V 3 1.5 1.5 1.5 Set up the apparatus as shown…. ..measure the voltage at the locations shown. What do you notice about your readings? For a parallel circuit, the voltage across the cell/battery is the same as the voltage across each branch. V 1 = V 2 = V 3 V 3 V 2 V 1 Voltage (V) Voltmeter