Electric circuits Flashcards
What is the equation for charge?
Charge (C) = current (A) x time (s)
This equation relates the amount of electric charge to the current flowing and the time duration.
What is the equation for energy transferred?
Energy transferred (J) = charge (C) x voltage (V)
This formula is used to calculate the energy transferred in an electric circuit.
What is the equation for voltage?
Voltage (V) = current (A) x resistance (Ω)
This equation describes the relationship between voltage, current, and resistance in a circuit.
Define electric current.
The rate of flow of charge
In metallic conductors, electric current is a flow of negatively charged electrons.
What is the unit of current?
Ampere (A)
One ampere flows when a charge of one coulomb passes a point in an electric circuit in one second.
Define coulomb.
The unit of charge
One coulomb per second is equal to one ampere.
What happens to current in a series circuit?
The current is the same everywhere
In a series circuit, the total current remains constant despite the number of components.
How does increasing the number of cells affect current in a series circuit?
Increases the current everywhere
More cells provide more energy, thus increasing the current flow.
What is the effect of adding more components in a series circuit?
Decreases the current everywhere
Additional components increase resistance, which reduces current.
What is a series circuit?
Components connected one after each other
In this configuration, the same current flows through all components.
What is a parallel circuit?
Components connected on separate branches of the circuit
In a parallel circuit, the voltage across each component is the same.
What happens to total voltage in a series circuit?
Total voltage across all components sums to the voltage across the battery
This means that the total voltage drop equals the source voltage.
What occurs to current in a parallel circuit?
Current splits into multiple paths through different branches.
What is the relationship between total current entering and leaving a junction in a parallel circuit?
Total current entering a junction = total current leaving the junction.
What voltage do branches in parallel receive?
Branches in parallel receive the same voltage.
What happens to voltages along a simple path through the branches in a parallel circuit?
Voltages along the way add up to the total voltage from the cell.
How is an ammeter connected in a circuit?
Ammeters are connected in series.
What does an ammeter measure?
An ammeter measures the current at that spot.
How is a voltmeter connected in a circuit?
A voltmeter is connected in parallel.
What does a voltmeter measure?
A voltmeter measures the voltage across the component.
What is true about components in a series circuit?
All components get the same current but share the voltage.
What happens if one component breaks in a series circuit?
If one component breaks, all the other components don’t work.
What is true about components in a parallel circuit?
All components receive the same voltage and can be switched on and off individually.
What happens if one component breaks in a parallel circuit?
If one breaks, the others still work.
Why is current conserved in a circuit?
Electrons can’t be created or destroyed; total amount of electrons must remain the same.
What is the unit of energy?
Joule (J).
What is the relationship between watts and joules?
A watt (W) is joules per second.
What is voltage measured in?
Volts (V).
What does the voltage represent when a charge of one coulomb passes through a point?
The energy provided.
What is the formula for energy transferred?
Energy transferred (J) = charge (C) x voltage (V)
Fill in the blank: Voltage is equal to _______.
the energy provided when a charge of one coulomb passes through a point.
True or False: In a parallel circuit, if one component fails, all other components stop working.
False.
What is the formula for energy in an electrical context?
Energy = current x time x voltage
E = itv
What is resistance in electrical terms?
Resistance is the opposition that an electrical device has to the flow of electrical current
How is resistance calculated?
Resistance = voltage / current
In what unit is resistance measured?
Ohms
What is a resistor?
A component that can impede the flow of electrons
What is a variable resistor?
A component whose resistance can be changed
What is the relationship between voltage, current, and resistance?
Voltage (V) = current (A) x resistance (Ω)
What happens to current when resistance increases?
Current decreases
What happens to current when resistance decreases?
Current increases
What type of resistance allows large currents to flow?
Low resistance
What type of resistance allows small currents to flow?
High resistance
What type of wires have a large resistance?
Long thin wires
What type of wires have a small resistance?
Short thick wires
What unit measures electric current?
Amps (A)
Amperes are the standard unit for measuring electric current.
What is the unit for electric charge?
Coulomb (C)
Coulombs quantify the amount of electric charge.
What unit measures energy in electrical systems?
Joule (J)
Joules are used to express energy in electrical contexts.
What is the unit of electrical resistance?
Ohm (Ω)
Ohms measure the opposition to current flow in an electrical circuit.
What unit measures time in electrical contexts?
Second (s)
Seconds are the standard unit of time.
What is the unit for voltage?
Volt (V)
Volts measure the electric potential difference.
What unit measures electrical power?
Watt (W)
Watts quantify the rate of energy transfer.
What does an open switch symbol indicate in a circuit diagram?
Open circuit
An open switch means the circuit is incomplete and current cannot flow.
What does an ammeter measure?
Current
Ammeters are used to measure the flow of electric current.
What is the purpose of a fuse in an electrical circuit?
Protect against overloads
Fuses prevent excessive current from flowing, which can cause damage.
What does LED stand for?
Light Emitting Diode
LEDs are semiconductor devices that emit light when current flows through them.
What does a voltmeter measure?
Voltage
Voltmeters are used to measure the electric potential difference between two points.
What is a thermistor?
Temperature-sensitive resistor
Thermistors change resistance with changes in temperature.
What does a closed switch symbol indicate in a circuit diagram?
Closed circuit
A closed switch means the circuit is complete and current can flow.
What is the role of an LDR?
Light-dependent resistor
LDRs change resistance based on the amount of light they are exposed to.
What is the risk of electrocution?
Contact with live wire
Electrocution can occur if the current exceeds 100 mA across the heart.
What can cause a fire in electrical systems?
Excessive current flow
Too much current can heat wires, leading to fires.
What is insulation in electrical safety?
Use of non-conductive materials
Insulation protects users from electric shock.
What is double insulation?
Insulation with an earth wire
Double insulation provides an extra safety measure by grounding the device.
What is the primary function of fuses?
Fuses melt when experiencing too much current, creating a gap in the circuit to prevent sparks and fires.
How do circuit breakers differ from fuses?
Circuit breakers react faster and can be reset by closing a switch again.
What is the purpose of an earth wire in appliances with metal cases?
An earth wire provides a low resistance path to the ground, preventing electric shock from a live wire touching the metal casing.
Define electric current.
Electric current is the rate of flow of charge.
Define electric resistance.
Electric resistance is a measure of how hard it is for current to flow through a compound.
What does a resistance of 1 Ohm signify?
A voltage of 1 volt is required to push a current of 1 Amp through a component.
What is the formula for voltage?
Voltage = current x resistance.
How can resistance of a component be measured?
Using a voltmeter connected in parallel and an ammeter with a variable resistor connected in series.
What characterizes an Ohmic component?
An Ohmic component obeys Ohm’s law, meaning its resistance is constant regardless of current or voltage.
What is the graphical representation of Ohmic components?
A straight line through the origin on a graph of current against voltage.
Give examples of Ohmic components.
- Wires
- Resistors
How does an electric current affect resistors?
Particles collide, transferring energy which heats up the resistor and increases resistance. This increases resistance as the particles vibrate more meaning there is less space for current to flow. It can get hot enough to melt and stop the circuit from working.
They can be used in domestic things such as toasters to cook bread.
True or False: Non-ohmic resistors have constant resistance.
False
Fill in the blank: Voltage = _______ x resistance.
[current]
What happens to current as voltage increases in a filament lamp?
Current increases as voltage increases
This is because electrons are pushed harder around the circuit.
How does the resistance of a filament lamp change with voltage?
Resistance increases as voltage increases
This is due to the temperature increase causing electrons to vibrate more and collide more, making it harder for them to flow.
What is the relationship between current and voltage in an ohmic conductor?
Current is directly proportional to voltage
This holds true in a wire at a constant temperature.
What is the behavior of resistors at a constant temperature regarding current and voltage?
Current is directly proportional to voltage
Different resistors with different resistances will have different gradients.
What is a diode?
A component that allows current to flow in one direction only
The current increases as voltage increases in the positive quadrant.
What occurs in the negative quadrant of a diode’s current-voltage graph?
There is no current
Current only flows when the voltage is positive.
What type of devices are thermistors and LDRs?
They are semiconductor devices
Their resistance changes with temperature and light exposure.
What happens to the resistance of a thermistor when it heats up?
Resistance decreases
Electrons gain enough energy to escape their chemical bonds and conduct.
What effect does increased light have on the resistance of an LDR?
Resistance decreases
More light allows electrons to gain enough energy to escape from their chemical bonds and conduct.
What does the resistance of a thermistor depend on?
Temperature
In hot conditions, the resistance is low, while in cool conditions, the resistance is high.
How does temperature affect electron movement in a thermistor?
At low temperatures, electrons have less energy and move less, resulting in more resistance.
What happens to current as resistance increases in a thermistor?
Current decreases.
What is a common application of a thermistor?
Temperature detectors, e.g., thermostats.
What does LDR stand for?
Light Dependent Resistor.
How does light intensity affect the resistance of an LDR?
In bright light, resistance is low; in darkness, resistance is high.
What is a common use of an LDR in electronic circuits?
Street lighting.
What is the formula for electrical power?
Power = current x voltage.
How can electrical power also be defined in terms of energy?
Power = energy transferred / time.
What does electrical power represent?
The rate at which an appliance transfers energy.
What is the relationship between power and energy transferred?
Energy transferred = power x time.
What is the voltage of mains electricity typically around?
230 V.
What does A.C. stand for and how does it behave?
Alternating Current; the current constantly changes direction.
What does D.C. stand for and how does it behave?
Direct Current; the current only flows in one direction.
What do lamps and LEDs indicate in a circuit?
The presence of a current.
When do Light Emitting Diodes (LEDs) light up?
When current flows through them in the right direction.
List some common applications of LEDs.
- Phone screens
- TV screens
- Traffic lights
- Energy saving bulbs.
