The potential difference or voltage, V across two points is defined as the energy, E dissipated or transferred by a coulomb of charge, Q that moves through the two points.
Therefore, potential difference,
Current is the rate of charge flow. Therefore, the total charges that flow through the two points is given as:
Since the energy dissipated Or transferred is given by:
Therefore, the relationship between E, V, I and t can be written as:
Thus, the formulae for the energy dissipated or released by electric charges may be written in three different ways. The one that is chosen depends on the information given.
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Relationship between Power Voltage and Current
Power is defined as the rate of electrical energy dissipated or transferred. Hence
Power is measured in joule per second (J/s) and the unit for power is watt The power of 1 watt means that 1 joule of electrical energy is being dissipated or released in every second.
Relationship between Energy Transferred, Current, Voltage and Time Problems with Solutions
- A current of 5 A flows through an electric heater when it is connected to a 240 V mains supply. How much heat is released after 2 minutes?
E = VIt
= 240 x 5 x 2 x 60 J
= 144 000 J
- Two resistors of 5 Ω and 10 Ω respectively are connected in parallel to a 9 V supply.
(a) The ratio of the power dissipated (used up) in the 5 Ω resistor to the 10 Ω resistor.
(b) The power output of the supply.