Electric Circuits Flashcards
What is static electricity?
When an object becomes electrically charged.
What happens with friction?
Electrons are transferred from one object to another.
What happens when you rub a polythene rod?
The electrons are transferred from to the rod from the cloth. The rod becomes negatively charged.
What happens when you rub a Perspex rod with a cloth?
Electrons are transferred from the rod to the cloth. The rod becomes positively charged. It’s positive charge is equal to the negative charge of the dry cloth.
What is an electric field?
Two charged objects exert a non-contact force on each other because of this charge. The charged object creates an electric field around itself. The second charge object experiences a charge because of this field.
What is an electric current?
A flow of charge. Millions of an electron pass through a cell every second.
What determines the size of an electric current?
The rate of flow of electric charge. The bigger the amount of electrons that passes through a component each second, the bigger is the current passing through it.
What is the current like in a single, closed group circuit?
It is the same at any point in the circuit. This is because the number of electrons that passes through any part of the circuit is the same way any other part.
What is an electric current of one ampere equal to?
Rate of flow of charge of one coulomb.
What is a diode?
It allows the current through it in a certain direction and only when it is connected.
What is potential difference?
The energy transferred to the bulb or work done on it by each coulomb of charge that passes rough it.
What does a resistor do?
Limits the current.
Why is a wire called an ohmic conductor?
It’s resistance stays constant as the current changes.
What happens to the resistance of the filament lamp as the temperature increases?
The resistance increases. The resistance of any metal increases and the temperature increases. This is because the atoms in the metal filament begin to vibrate and this means that they resist the passage of electrons through the filament more.
What is a LED?
A diode that emits light when a current flows through it.
What is a thermistor?
A temperature dependent resistor. It’s resistance decreases if its increases.
What happens to the resistance in a light dependent resistor?
The resistance decreases as the light intensity increases.
What is the rule about the current in a series circuit?
In a series circuit, the same current passes through each component.
What is the rule about p.d. in a series circuit?
The total potential difference (of the power supply) is shared between components
The total p.d. of cells in series is the sum of the p.d. of each cell.
What is the rule about resistance in series?
The total resistance of two or more components in series is equal to the sum of the resistance of each component.
What happens when you add more resistors in series?
It increases the total resistance of the circuit.
This is because the total p.d. is shared between more resistors.
What is the rule about current in parallel circuits?
The total current through the whole circuit is the sum of the currents through separate branches.
What is the rule of p.d. In parallel circuits?
For components in parallel, the p.d. across each components is the same.
What happens when you add more resistors in parallel?
The total resistance of two (or more) components in parallel is less than the resistance of the resistor with the least resistance.
Why does adding more resistors in parallel decrease the total resistance?
Adding an extra resistor decrease the total resistance of the circuit because the total p.d. is the same across each resistor. So adding an extra resistor in parallel increases the total current entering combination.
What is potential difference?
A potential difference of one volt tells us that one joule of energy is transferred for each coulomb of charge.
What way does the current flow in a circuit?
negative to positive
What is the current
flow of electrical charge
How do you draw the conventional current?
The arrow pointing from positive to negative. Opposite direction.
How do you measure the current?
Using an ammeter
What will the reading be on multiple ammeters in a series circuit?
The same. The current is never used up.
What happens to the current in parallel circuits?
The current splits
The current in the branches adds up to the total current leaving the cell.
What is potential difference?
The amount of energy transferred per each coulomb of charge. Measured in volts.
How do you measure potential difference?
Place the voltmeter parallel to the component.
Explain the pd in series circuits..
The pd is shared so the pf across each component adds up to the total pd. If you add in more lamps, they will be dimmer because of this.
What is the potential difference for components connected in parallel?
For components connected in parallel, the potential difference across each component is the same.
What is a battery?
Two or more cells connected together. The pd of cells adds up to give us the total pd of the battery.
What is charge measured in?
Coulombs
What does a current of one ampere mean?
One coulomb of charge flowing per second. The size of the electric current is the rate of flow of electrical charge.
