PHYSICS
FORM 5
ELECTRICAL QUANTITES
QUANTITY SYMBOL UNIT SYMBOL
Current I Amperes A
Voltage (P.D.) V Volts V
Resistance R Ohm Ω
Charge (electric) Q Coulomb C
Power P Watt W
Energy E Joule J
Time T seconds s
Quantity of a Charge, Q
𝑄 = 𝐼𝑡
𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑐ℎ𝑎𝑟𝑔𝑒 = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 × 𝑡𝑖𝑚𝑒
𝐶𝑜𝑢𝑙𝑜𝑚𝑏 = 𝐴𝑚𝑝𝑒𝑟𝑒 × 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏 = 1 𝐴𝑚𝑝𝑒𝑟𝑒 × 1 𝑠𝑒𝑐𝑜𝑛𝑑
Definition of a Coulomb – The coulomb is defined as the quantity of charge which flows in one
second passed any point in a circuit in which there is a steady current of 1 ampere.
Since, 𝑄 = 𝐼𝑡, transposing to make I the subject,
𝑄
𝐼=
𝑡
𝐶𝑜𝑢𝑙𝑜𝑚𝑏
𝐴𝑚𝑝𝑒𝑟𝑒 =
𝑡𝑖𝑚𝑒
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 𝐴𝑚𝑝𝑒𝑟𝑒 =
1 𝑠𝑒𝑐𝑜𝑛𝑑
Definition of an Ampere – A current of one ampere is a flow of charge at a rate of 1 Coulomb
per second.
, PHYSICS
FORM 5
ELECTRICAL QUANTITES
Voltage
The voltage or potential difference between the ends of a conductor is equal to the energy
converted from electrical to other forms of energy per unit electric charge flowing through it.
𝐸𝑛𝑒𝑟𝑔𝑦
𝑉𝑜𝑙𝑡𝑎𝑔𝑒 =
𝐶ℎ𝑎𝑟𝑔𝑒
𝐸
𝑉=
𝑄
𝐽𝑜𝑢𝑙𝑒𝑠
𝑉𝑜𝑙𝑡𝑠 =
𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 𝐽𝑜𝑢𝑙𝑒
1 𝑉𝑜𝑙𝑡 =
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 volt is defined as the potential difference between the ends of a conductor if 1 Joule of
electrical energy is converted to other forms of energy when one Coulomb of charge flows
through it.
Resistance
Resistance is the ability of a substance to resist the flow of a current through it.
𝑉𝑜𝑙𝑡𝑎𝑔𝑒
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 =
𝐶𝑢𝑟𝑟𝑒𝑛𝑡
𝑉
𝑅=
𝐼
𝑉𝑜𝑙𝑡𝑠
𝑂ℎ𝑚𝑠 =
𝐴𝑚𝑝𝑒𝑟𝑒𝑠
1 𝑉𝑜𝑙𝑡
1 𝑂ℎ𝑚 =
1 𝐴𝑚𝑝𝑒𝑟𝑒
Definition of an Ohm – 1 Ohm is defined as the resistance of a conductor through which a
current of 1 ampere flows when the potential difference of 1 volt is applies across its ends.
FORM 5
ELECTRICAL QUANTITES
QUANTITY SYMBOL UNIT SYMBOL
Current I Amperes A
Voltage (P.D.) V Volts V
Resistance R Ohm Ω
Charge (electric) Q Coulomb C
Power P Watt W
Energy E Joule J
Time T seconds s
Quantity of a Charge, Q
𝑄 = 𝐼𝑡
𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑐ℎ𝑎𝑟𝑔𝑒 = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 × 𝑡𝑖𝑚𝑒
𝐶𝑜𝑢𝑙𝑜𝑚𝑏 = 𝐴𝑚𝑝𝑒𝑟𝑒 × 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏 = 1 𝐴𝑚𝑝𝑒𝑟𝑒 × 1 𝑠𝑒𝑐𝑜𝑛𝑑
Definition of a Coulomb – The coulomb is defined as the quantity of charge which flows in one
second passed any point in a circuit in which there is a steady current of 1 ampere.
Since, 𝑄 = 𝐼𝑡, transposing to make I the subject,
𝑄
𝐼=
𝑡
𝐶𝑜𝑢𝑙𝑜𝑚𝑏
𝐴𝑚𝑝𝑒𝑟𝑒 =
𝑡𝑖𝑚𝑒
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 𝐴𝑚𝑝𝑒𝑟𝑒 =
1 𝑠𝑒𝑐𝑜𝑛𝑑
Definition of an Ampere – A current of one ampere is a flow of charge at a rate of 1 Coulomb
per second.
, PHYSICS
FORM 5
ELECTRICAL QUANTITES
Voltage
The voltage or potential difference between the ends of a conductor is equal to the energy
converted from electrical to other forms of energy per unit electric charge flowing through it.
𝐸𝑛𝑒𝑟𝑔𝑦
𝑉𝑜𝑙𝑡𝑎𝑔𝑒 =
𝐶ℎ𝑎𝑟𝑔𝑒
𝐸
𝑉=
𝑄
𝐽𝑜𝑢𝑙𝑒𝑠
𝑉𝑜𝑙𝑡𝑠 =
𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 𝐽𝑜𝑢𝑙𝑒
1 𝑉𝑜𝑙𝑡 =
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏
1 volt is defined as the potential difference between the ends of a conductor if 1 Joule of
electrical energy is converted to other forms of energy when one Coulomb of charge flows
through it.
Resistance
Resistance is the ability of a substance to resist the flow of a current through it.
𝑉𝑜𝑙𝑡𝑎𝑔𝑒
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 =
𝐶𝑢𝑟𝑟𝑒𝑛𝑡
𝑉
𝑅=
𝐼
𝑉𝑜𝑙𝑡𝑠
𝑂ℎ𝑚𝑠 =
𝐴𝑚𝑝𝑒𝑟𝑒𝑠
1 𝑉𝑜𝑙𝑡
1 𝑂ℎ𝑚 =
1 𝐴𝑚𝑝𝑒𝑟𝑒
Definition of an Ohm – 1 Ohm is defined as the resistance of a conductor through which a
current of 1 ampere flows when the potential difference of 1 volt is applies across its ends.
