electricity Flashcards
What are the two ways of joining electrical components?
in series and in parallel
In a series circuit, what is the current like at any point?
the same value at any point
What happens to the current when the voltage of the power source increases in a series circuit?
current increases
What is a parallel circuit?
a circuit that has two or more loops or more than one path that electrons can take
What happens to the current at a junction in a parallel circuit?
current splits at a junction
True or False: The amount of current flowing into a junction is equal to the amount flowing out.
True
What is the relationship between the current in individual branches and the total current in a parallel circuit?
the sum of the current in the individual branches is equal to the total current
In a series circuit, how does the total voltage relate to the components?
the total voltage is shared between the components
What is the voltage across two identical components in a series circuit?
the same, equal to half the total voltage of the power supply
What is a key disadvantage of a series circuit?
if one component breaks, all other components stop working
What is the total resistance when resistors are connected in series?
the sum of their individual resistances
How does the total voltage in a series circuit relate to the individual voltages across resistors?
the total voltage is the sum of the voltages across each individual resistor
What happens to the total resistance when more resistors are added in series?
it increases
In a parallel circuit, how does the voltage across each branch compare to the power supply voltage?
the total voltage across each branch is the same as the voltage of the power supply
What happens to the current in a parallel circuit if one component breaks?
the others will continue to function
What is the equation for combined resistance in a series circuit?
R = R1 + R2 + R3
What characterizes linear IV graphs?
the IV graph is a straight line which passes through the origin
What does a non-linear IV graph indicate about resistance?
the resistance is not constant
What is the relationship between current and voltage for a fixed resistor?
the relationship is linear or directly proportional
What type of resistor has a resistance that changes based on the length of wire?
variable resistors
Thermistors have resistance that depends on what factor?
temperature
What is the behavior of resistance in a thermistor as temperature increases?
the resistance decreases
What happens to the resistance of an LDR in bright conditions?
the resistance is low
Fill in the blank: The current is the flow of ______.
electrons
True or False: Current in a parallel circuit splits equally among branches.
False
What is the effect of increasing the number of components in a series circuit?
total resistance increases, hence less current flows
How is the total resistance in a parallel circuit compared to the resistance of individual components?
the total resistance is less than that of each component
What type of components can have non-linear IV graphs?
filament lamps, diodes, LDRs, thermistors
What happens to the current in a diode during reverse bias?
no current flows
What happens to the resistance of a thermistor as temperature increases?
The resistance of a thermistor decreases
The relationship is inversely proportional.
How does the resistance of a thermistor depend on temperature?
The resistance of a thermistor depends on its temperature
This relationship can be represented graphically.
What is the relationship between resistance and temperature for a thermistor shown on a graph?
The graph shows a curve indicating that resistance and temperature are inversely proportional
This means as one increases, the other decreases.
What is a light-dependent resistor (LDR)?
A light-dependent resistor (LDR) is a device whose resistance depends on light intensity
It is used in various applications to detect light levels.
What happens to the resistance of an LDR in dark conditions?
The resistance of an LDR is high in dark conditions
This contrasts with its behavior in bright conditions.
What is the relationship between light intensity and resistance in an LDR?
As light intensity increases, the resistance of an LDR decreases
Conversely, as light intensity decreases, the resistance increases.
How is the relationship between light intensity and resistance for an LDR represented graphically?
The graph shows a curve indicating that light intensity and resistance are inversely proportional
Similar to the thermistor’s graph.
What do lamps and LEDs do when current flows through them?
They illuminate (light up) when a current flows through them
This indicates the presence of current in a circuit.
What type of component is an LED?
An LED is a type of diode
It allows current to flow in only one direction.
What must be considered for an LED to light up in a circuit?
An LED will only light up if it is placed in the correct direction
This is due to its diode nature.
What is the circuit symbol for an LED?
The circuit symbol for an LED is a specific design that represents its function
It is important to learn the symbols for exams.
How do you distinguish between light-dependent and light-emitting symbols in circuit diagrams?
Two arrows pointing towards a symbol mean it is light-dependent; two arrows pointing away mean it is light-emitting
This differentiation is crucial for understanding circuit diagrams.
What is the significance of circles around circuit symbols?
Circles around symbols are often optional but denote specific components like meters and bulbs
Understanding these details is important for accurate representation.
What is electric current defined as?
The rate of flow of electric charge.
In what units is current measured?
Amperes or amps (A).
1 amp is equivalent to how much charge flowing in how much time?
1 coulomb flowing in 1 second.
What forms when a circuit is created?
Current flows.
From which terminal to which terminal does current flow?
From the positive terminal to the negative terminal.
How can current be measured?
Using an ammeter.
How must ammeters be connected to measure current?
In series with the component being measured.
What material are wires in electric circuits typically made of?
Metal.
What is the flow of current in metal wires composed of?
Negatively charged electrons.
What is conventional current?
The flow of positive charge from positive to negative terminal.
What is the equation relating current, charge, and time?
Q = I × t.
What does Q represent in the equation Q = I × t?
Charge, measured in coulombs (C).
What does I represent in the equation Q = I × t?
Current, measured in amps (A).
What does t represent in the equation Q = I × t?
Time, measured in seconds (s).
What is voltage defined as?
The energy transferred per unit charge passing between two points.
In what units is voltage measured?
Volts (V).
1 volt is equivalent to how much energy transferred by how much charge?
1 joule of energy by 1 coulomb of charge.
How can voltage be measured?
Using a voltmeter.
How must voltmeters be connected to measure voltage?
In parallel with the component being measured.
What is the equation linking energy transferred, voltage, and charge?
E = Q × V.
What does E represent in the equation E = Q × V?
Energy transferred, measured in joules (J).
What does V represent in the equation E = Q × V?
Voltage, measured in volts (V).
What is resistance defined as?
The opposition of a component to the flow of electric current through it.
In what units is resistance measured?
Ohms (Ω).
What is the relationship between resistance and current for a given voltage?
The higher the resistance, the lower the current; the lower the resistance, the higher the current.
What is the equation relating voltage, current, and resistance?
V = I × R.
What does R represent in the equation V = I × R?
Resistance, measured in ohms (Ω).
Calculate the voltage across a resistor of 10 Ω with a current of 0.3 A.
3 V.
What is electrical power defined as?
The rate of energy transfer or the amount of energy transferred per second.
What factors determine the electrical power of a device?
- Voltage (potential difference) of the device
- Current of the device.
What is the formula for electrical power?
P = IV
What do the symbols in the power equation P = IV represent?
- P = power, measured in Watts (W)
- I = current, measured in amperes (A)
- V = potential difference, measured in volts (V).
What is the unit of power?
The Watt (W), which is equivalent to a joule per second (J/s).
What is a fuse?
A safety device designed to cut off the flow of electricity to an appliance if the current becomes too large.
What happens to a fuse when the current becomes too large?
The wire heats up and melts, breaking the circuit and stopping the current.
What sizes do fuses typically come in?
- 3 A
- 5 A
- 13 A.
How do you select the appropriate fuse for an appliance?
Choose a fuse with a current rating slightly higher than the current needed by the appliance.
What is the equation for calculating energy transferred?
E = P × t
What does the equation E = I × V × t represent?
The energy transferred by electrical work in a component or appliance.
What is the relationship between work done and energy transferred?
Work done is equal to the energy transferred.
What is the potential hazard of mains electricity?
Potential differences as small as 50 V can pose a serious hazard.
What are common electrical safety hazards?
- Damaged insulation
- Overheating of cables
- Damp conditions.
What safety features are built into domestic appliances?
- Double insulation
- Earthing
- Fuses
- Circuit breakers.
What is double insulation?
A safety feature where appliances have two layers of insulation: insulation around the wires and a non-metallic case.
What does the earth wire do?
Provides a low resistance path to the earth, reducing the risk of electrocution.
What is the main advantage of circuit breakers over fuses?
They can be reset and used again, and they work much faster.
How does a resistor heat up?
Due to the collisions of free electrons within the wire as current passes through.
What is direct current (d.c.)?
A steady current, constantly flowing in the same direction in a circuit.
What is alternating current (a.c.)?
A current that continuously changes its direction, going back and forth around a circuit.
What is the frequency of UK mains electricity?
50 Hz.
What is the potential difference of UK mains electricity?
Around 230 V.
What is the difference between direct current and alternating current?
- Direct current: continuous and in one direction
- Alternating current: constantly changing direction.
hazards
water in contact , water conducts electricity causing shock.
appliance with heating element reaches high temperature, insulation can melt and causing a fire.
damaged equipment, live wire cant be exposed or it can cause shock. microwave leaking can leak radiation.
trip hazards
overloaded cables or sockets, circuits should have correct fuses or it can cause fire
how does a earth wire act as a safety feature
earth connected to metal casing
provide low resistance path to earth
large current in earth wire
hence fuse breaks
circuit switches off or current stops
why do we need earth wire
when there’s a metal case it can conduct electricity since its metal. earth wire prevents user from shock.
voltage across thermistor (actually know this)
voltage across thermistor + voltage across
fixed resistor = voltage across cell
mA to A
divide by 1000
