Electricity Flashcards
In a cell which side is the positive terminal?
Left side.
An atom contains two types of charged particles
-Proton (+1)
-Electron (-1)
What are the differences between series and parallel circuits in regards to current and voltage?
Series:
-Same current flows throughout
-Voltage is not the same. Total is equal to the sum of potential differences across each component
Parallel:
-Current flowing in a junction is equal to the current leaving it.
-The sum of the currents in each section is equal to the total curent
-The voltage across each branch is the same
Where must a voltmeter be placed in a circuit?
In parallel to the component that is being measured.
Give an equation linking voltage, energy transferred, and charge.
V=E/Q
E/V x Q
A volt can also be describes as a…
Joule per coulomb
What is current
The rate of flow of charge in a certain amount of time
What is an ammeter and where must it be connected in a circuit?
Measures current. It is places in a series with the component it is required to measured.
Equation including time, current and charge
Q = I x T
Q/IT
Q=Charge (coulombs)
T=Time (s)
I= Current (amps)
State the equation linking current, voltage, resistance with their units.
V=I x R
V/IR
I=Current (amps)
R=Resistance (Ohms)
How does changing the resistance in a circuit change the current?
-Current is inversely proportional to resistance. Therefore at a constant voltage, increasing the resistance will decrease the current.
-In an electrical circuit the flow of electrons causes a current. A high resistance makes it harder for electrons to pass through and therefore reduces the current.
How can you use a variable resistor to increase the current in a series circuit?
You set the variable resistor to have a lower resistance, this should increase the current
Explain why when two resistors are in series the overall resistance increases
-Current in each of them is the same I1=12=1T
-Total voltage=The sum of the voltage across each resistor.
Therefore as V1=IT X R1 and V2=I2 X R2 then VT= (IT X R1)+(IT X R2) which can be written as VT=IT(R1+R2). Also VT=IT X RT
Therefore RT=R1 + R2
Therefore the overall resistance increases as you add resistors in series.
Why does the net resistance of two resistors in parallel decrease?
In parallel:
-IT=I1+I2+I3
-V1=V2=V3
Therefore 1/RT=1/R1+1/R2+1/R3
Explain the relationship between voltage, current and resistance in a filament lamp.
As temperature increases in the lamp the resistance also increases. This is because a higher temperature makes the ions in the filament vibrate more, making it harder for electrons to pass through. This therefore decreases the current. If voltage is doubled, current will not be doubled.
How do diodes work?
A diode only allows current to flow in one direction. If current is flowing in the right way, the resistance is large at small voltages, but ay higher voltages the resistance becames very small.
Describe the relationship between thermistors and resistance.
The resistance of a thermistor changes with temperature, when the temperature increases the resistance decreases.
How does a Light Dependent Resistor work?
The resistance of a LDR varies with light. As the light intensity increases, the resistance decreases.
When an electrical current flows through a resistor why does it light up?
There are collisions between the electrons and the ions in the resistor’s lattice. This causes a transfer of kinetic energy into thermal energy which is released into the surroundings.