Chapter 10 - Electricity Flashcards
What is the test to find out if something is a conductor or an insulator ?
Join it across a bulb and a battery, if the bulb lights its a conductor, if not its an insulator
Name 3 good conductors:
Gold , silver , copper , graphite
Name 3 insulators
wool, rubber , polythene, wax , glass
How does a cell connected to a conductor move electrons ?
the electrons are attracted to the positive end of the cell and are repelled from the negative end of the cell
Which way does conventional current flow ?
From positive to negative
Which way do electrons flow ?
From negative to positive
Draw a circuit symbol for a : switch , cell, battery and a resistor.
Please (page 134)
Draw a circuit symbol for a : variable resistor, fuse and a voltmeter
Please (page 134)
Draw a circuit symbol for an : ammeter and lamp
Please (page 134)
What does the long thin line of the cell represent ?
The positive terminal
What happens if a cell is connected in the wrong way in a series circuit ?
It cancels the affect of one other battery E.g. 3 1.5V battery’s connected in series if two are connected properly and one is connected the wrong way the total voltage will be 1.5V
What is the unit of charge ?
Coulomb (C)
What is the unit of current ?
Ampere (A)
How many milliamperes in 1 ampere ?
1000 mA = 1 A
How many microamperes in 1 ampere ?
1000000 uA = 1A
What is the equation for charge ?
Q = I x t charge = current x time
What are the two conditions for an electric current to flow ?
- no gaps in the circuit
- source of energy so that the charge may move
What is the equation for resistance ?
R = V/I
What is resistance measured in ?
ohms
How do you find the total resistance in a series circuit ?
The resistance is simply the sum of the individual resistances of the resistors
How do you find the resistance of two resistors connected in parallel ?
R total = R1 x R2 / R1 + R2
‘product over sum’ formula
How do you find the resistance of three or more resistors connected in parallel ?
1 1 1 1
—- = – + – + –
Rtotal R1 R2 R3
What happens regarding to current and voltage in series circuits ?
- the current across each resistor is the same
- the sum of the voltages across each resistor is equal to the battery or power supply voltage
What happens regarding to current and voltage in parallel circuits ?
- the voltage across each resistor is the same as the voltage provided by the battery
- the sum of the currents in each resistor is equal to the current coming from the battery
