Energy Flashcards
What factors affect the energy transferred when
charge flows through a component?
● Amount of charge
● The potential difference across the
component
Give an equation linking energy, current and p.d.,
giving all SI units
energy (J) = p.d. (V) x current (A) x time (s)
E = VIt
Define potential difference in terms of charge
The work done per unit charge
Give an equation relating potential difference to
charge
energy transferred (J) = charge (C) x p.d. (V)
E = QV
When an electrical current flows through a resistor why does it heat up?
There are collisions between the electrons and the ions in the resistor’s lattice. This causes a transfer of kinetic energy into thermal energy, which is released into the surroundings
How do low resistance wires reduce unwanted energy transfers?
A smaller resistance will mean there are fewer collisions, therefore less energy will be wasted through heating
What are some advantages of the heating effect?
It is useful for appliances such as
toasters or electrical fires, where the
heat is the desired product.
What are some advantages and disadvantages of
the heating effect?
● The loss of energy as heat energy can
make an appliance inefficient
● If an appliance overheats it can catch fire or
overheat, which could ruin the device or
injure the user
The energy transferred per second is also known
as…
Power
Define Power
The rate of energy transfer, or the rate at which work is done
What are the units of power?
Watts, W
Give an equation linking power and
potential difference, giving all SI units
power (W) = current (A) x p.d. (V)
Give an equation to work out power
without p.d., giving all SI units
power (W) = current² (A) x resistance (Ω)
P = I²R
Give an equation linking power and energy, giving all
SI units
power (W) = energy (J) ÷ time (s)
Give equations linking power and resistance, including all SI units
power (W) = current² (A) x resistance (Ω)
P = I² x R
power (W) = p.d.² (V) ÷ resistance (Ω)
P = V² ÷ R
