P4 Electric Circuits Flashcards
What does the circuit diagram for an open switch look like
Two circles with a line that doesn’t connect them
What does the circuit diagram for a thermistor look like
A box with a hockey stick through it
What does the circuit diagram for a lamp look like
A circle with a cross-hair
What does the circuit diagram for a closed switch look like
Two circles with a line that connects them
What does the circuit diagram for a cell look like
A long thin and short thick line
What does the circuit diagram for an ammeter look like
A circle with an “A”
What does the circuit diagram for a fuse look like
A box with the wire running through it
What does the circuit diagram for ground look like
Three lines decreasing in size
What does the circuit diagram for a voltmeter look like
A circle with a “V”
What does the circuit diagram for a wire look like
A line
What does the circuit diagram for a resistor look like
A box
What does the circuit diagram for a light-dependant resitor look like
A box in a circle with arrows towards it
What does the circuit diagram for a variable resistor look like
A box with a diagonal arrow through it
What does the circuit diagram for a diode look like
A triangle and perpendicular line in a circle
What does the circuit diagram for a LED look like
A triangle and perpendicular line in a circle with arrows pointing away
What does the circuit diagram for a battery look like
Two cells (a long thin and short thick line) connected with a dotted line
What is electric current
The flow of electrical charges
What is electric current measured in
Amperes
How is the flow of charge calculated
Flow of charge (Q) = current (I) * time (t)
What is the value of current at every point in a single closed loop
The same
What does there need to be for an electrical charge to flow
A charge of potential difference
A complete circuit
What is electric charge measured in
Coulombs
What is an electrical conductor
A material that allows electric current to pass through it
What are examples of electrical conductors
All metals
What are electrical insulators
Material that doesn’t allow electric current to pass through it
What are examples of electrical insulators
Plastic
Glass
How do electrical conductors conduct electricity
They have lots of charges that are free to move
In a metal, the charges of the free to move are electrons
The flow of charges creates an electrical current
How do electrical insulators insulate electricity
They have no free electrons
No charges are free to move and carry a current
What is potential difference
The difference in the amount of energy that charge carriers have between two points in a circuit
Work done / coulomb of charge
What is potential difference measured in
Volts
What happens, in terms of energy when a charge passes, through an electrical component
Energy is transferred to the electrical component
How is potential difference calculated
P.D (V) = current (I) current * resistance (R)
P.D (V) = energy (J) / charge (Q)
What is a potential difference of one volt is equal to
One joule of energy being used by one coulomb of charge
What does an ammeter measure
The flow of current that passes through it
How are ammeters connected in a circuit
In series
What does a voltmeter measure
Potential difference between two points in a circuit
How are voltmeters connected in a circuit
In parallel
What is resistance
A measure of how difficult it is for current flow through a component
What is resistance measured in
Ohms Ω
What affects the size of current
Resistance inverse (in proportional)
Potential difference (in inverse proportion)
How is resistance calculated
Resistance (R) = voltage (V) / current (I)
How does resistance change, in terms of length of wire
The longer the wire, the higher the resistance
What does the current- voltage graph for a resistor tell us
It obeys Ohm’s law (I=V/R)
The slope is equal to 1/ resistance
The constant slope show that resistance is constant
What is a diode
A non-ohmic conductor that only allows current to flow through it in one direction
They act as rectifiers, looking alternating current when it changes direction
What is a rectifier
A component that turns an alternating current to a direct current
What is a thermistor
A component that changes resistance based on its temperature
As temperature increases, resistance decreases
What is a light dependent resistor
A component that changes resistance based on light intensity
As light intensity increases, resistance decreases
In which direction does charge flow
From the energy source through the rest of the circuit and it’s components
What do components do with the energy transferred to them by the flow of current
Transfers energy into the surroundings
How is power calculated
Power (P) = current (I) * p.d. (V)
Power (P) = current (I) ^2 * resistance (R)
How is total energy transfer calculated
Energy (E) = power (P) * time (t)
What is an ohmic conductor
A conductor that obeys Ohm’s law
What is the resistance like in an ohmic conductor
At a constant temperature, current ∝ potential difference across the resistor
This means that the resistance remain constant as the current changes
What is a series circuit
A circuit where all its components are connected on the same line as each other
What is current like in a series circuit
Current is the same at all points
How is total resistance in a series circuit calculated
R = R1 + R2 + R3 …
How is total potential difference in a series circuit calculated
V = V1 + V2 + V3 …
In a series circuit, what is the total voltage of energy sources equal to
Total potential difference across components
What is a parallel circuit
A circuit where components are connected on separate branches of wire to the energy source
What happens to current in a parallel circuit
It is split between the branches of the circuit
How is total current through the energy source in a parallel circuit calculated
Sum of the current through each of the branches
What happens to resistance in a parallel circuit
The combined resistance of two resistors in a parallel circuit is less than the resistance of either of the resistors by themselves
How is total resistance in a parallel circuit calculated
1 / total resistance = 1 / R1 + 1 / R2 + 1 / R3 …
What is potential difference like in a parallel-connected components
Potential difference across each parallel connected component is the same
What is an electric field
The area where charged objects are subject to the non-contact force of another charged object
What is an ion
A charged molecule or atom
What is the line of force
A line along which free positive charge moves along in an electric field
When do objects become charged
When they gain or lose electrons
What happens when an object loses electrons
It becomes positively charged
What happens when an object gains electrons
It becomes negatively charged
How is a spark produced
Potential difference causes a rapid transfer of charge
This energy is stored in an electrostatic store and produces of spark
What can rubbing two objects together cause
It can cause electrons to jump from one object to another
Both objects become charged
What are isolated objects
Objects with no conducting path to Earth
What is static electricity
The electric force between objects that have been in charged when electrons transfer from one to another
How does an object’s distance from a charged object affect the strength of the electric field
The closer the object is to the charged object, the stronger that electric field is
How does an object’s charge from a charged object affect the strength of the electric field
The higher the charge of the object, the stronger the electric field
