Unit 15 A and B-Electrical Circuits and their application
Section 1 – Electrical symbols, units and definitions
Components of the circuit Circuit symbols
• Cell
• Battery
• Switch
• filament lamp
• fixed resistor
• thermistor
• light emitting diode (LED)
• light-dependent resistor (LDR)
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, • rheostat
• capacitor
• voltmeter
• Ammeter.
Glossary of terms
Circuit component Description
Current The rate of flow of electrons that flow per second on an
electrical circuit. It is measured in ampere(A).Current is
represented by the symbol I. Electrons flow from negative to
positive charge.
Potential difference Potential difference is the pressure that comes from an
electrical power that pushes charged electrons through a
ciruit.Potential difference is measured in volts and is sometimes
called voltage. The formula used to calculate voltage is
voltage=current * resistance
electrical charge This is a quantitative measure that produces a force when
placed in a electromagnetic field. This is recorded in coulombs
(C).One coulomb of charge is equivalent to 1.602 * 1019 number
of electrons. The charge is calculated by charge = capacitance *
Voltage
Resistance Resistance is measured in ohms (Ω).It is the power used to
resist the current that flows through a circuit. It does this by
dividing the amount of potential difference that flows through
the circuit.1 unit of resistance is one amps of current that flows
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, through one volt of potential difference.
Conductance The potential of a substance that conducts electricity. It is
measured in siemes and is the reciprocal of the resistance. The
formula used to calculate conductance is
conductance=1/resistance
Electrical power Electrical power is the measure of the amount of electrical
energy that is transferred per unit of time. Power is measured in
watts(W)
Capacitance Capacitance is the ability of a component to collect and store
energy as a form of electrical charge. A capacitor collect energy
as current flows through the circuit. Capacitance is measured in
farads. The sub units are microfarad, nana farad, Pico farad and
femtofarad.
Current in terms of Current is the flow of mobile charge carries. Which means it
flow of mobile charge calculates the number if electron flowing through the circuit per
carriers second. The charge they carry can either be negative or
positive. They are mobile which means they are free o move.
Electromotive force as The electromotive force is the energy provided by a cell or
a measure of ratio of battery for each unit of charge passing through it. It is measured
energy supplied per in volts (V).It is equal to the potential difference across the
unit of charge circuit when there is no current flowing through the circuit. The
following formulas are used to calculate emf they are
emf=energy/charge and emf=current(resistance +internal
resistance)
Conductance and The higher the resistance the lower the density of electrons.
resistivity in relation to The lower the resistance the higher the density of electrons.
density of mobile The resistance is therefore inversely proportional to the density
carries of the free electron in the material
Section 2 - Electrical formulae and relationships
Circuit diagram Calculating of electrical quantities
Energy supplied A kettle has a power rating of 2200 watts
and is used for 80 seconds. Workout the
total energy transferred
Energy = Power x Time.
E= 2200 * 80 =176000W
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Section 1 – Electrical symbols, units and definitions
Components of the circuit Circuit symbols
• Cell
• Battery
• Switch
• filament lamp
• fixed resistor
• thermistor
• light emitting diode (LED)
• light-dependent resistor (LDR)
Page 1 of 27
, • rheostat
• capacitor
• voltmeter
• Ammeter.
Glossary of terms
Circuit component Description
Current The rate of flow of electrons that flow per second on an
electrical circuit. It is measured in ampere(A).Current is
represented by the symbol I. Electrons flow from negative to
positive charge.
Potential difference Potential difference is the pressure that comes from an
electrical power that pushes charged electrons through a
ciruit.Potential difference is measured in volts and is sometimes
called voltage. The formula used to calculate voltage is
voltage=current * resistance
electrical charge This is a quantitative measure that produces a force when
placed in a electromagnetic field. This is recorded in coulombs
(C).One coulomb of charge is equivalent to 1.602 * 1019 number
of electrons. The charge is calculated by charge = capacitance *
Voltage
Resistance Resistance is measured in ohms (Ω).It is the power used to
resist the current that flows through a circuit. It does this by
dividing the amount of potential difference that flows through
the circuit.1 unit of resistance is one amps of current that flows
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, through one volt of potential difference.
Conductance The potential of a substance that conducts electricity. It is
measured in siemes and is the reciprocal of the resistance. The
formula used to calculate conductance is
conductance=1/resistance
Electrical power Electrical power is the measure of the amount of electrical
energy that is transferred per unit of time. Power is measured in
watts(W)
Capacitance Capacitance is the ability of a component to collect and store
energy as a form of electrical charge. A capacitor collect energy
as current flows through the circuit. Capacitance is measured in
farads. The sub units are microfarad, nana farad, Pico farad and
femtofarad.
Current in terms of Current is the flow of mobile charge carries. Which means it
flow of mobile charge calculates the number if electron flowing through the circuit per
carriers second. The charge they carry can either be negative or
positive. They are mobile which means they are free o move.
Electromotive force as The electromotive force is the energy provided by a cell or
a measure of ratio of battery for each unit of charge passing through it. It is measured
energy supplied per in volts (V).It is equal to the potential difference across the
unit of charge circuit when there is no current flowing through the circuit. The
following formulas are used to calculate emf they are
emf=energy/charge and emf=current(resistance +internal
resistance)
Conductance and The higher the resistance the lower the density of electrons.
resistivity in relation to The lower the resistance the higher the density of electrons.
density of mobile The resistance is therefore inversely proportional to the density
carries of the free electron in the material
Section 2 - Electrical formulae and relationships
Circuit diagram Calculating of electrical quantities
Energy supplied A kettle has a power rating of 2200 watts
and is used for 80 seconds. Workout the
total energy transferred
Energy = Power x Time.
E= 2200 * 80 =176000W
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