Volt
Voltage = energy ÷ charge V = E/Q 1
Volt = 1 Joule / 1 Coulomb
1. Calculate
the voltage across a bulb if 20 C transfers 4 J of electrical energy. Draw an
energy transfer diagram.
V = 4
J ÷ 20 C = 0.2 V electrical à light + thermal
2. Calculate
the voltage across a dynamo if 600 J of energy is transferred by 25 C of
charge. Draw an energy transfer diagram. (How is it different from q1?)
V =
600 J ÷ 25 C = 24 V kinetic à electrical + heat here
another form of energy is transferred to
electrical wheras in q1 energy is transferred from electrical to other forms
3. A
bulb has a voltage of 6V across it. Calculate the energy is transferred by 90
C.
E = V
x Q = 6 V x 90 C = 540 J
4. A
train motor operates on a voltage of 25 kV (1kV = 1000 V). Calculate the charge
that transfers 800 kJ (1kJ = 1000 J)
of electrical energy.
Q = E
÷ V = 800000 J ÷ 25000 V = 32 C
5. A
torch bulb runs off a 1.5V cell (battery). Calculate the energy transferred by
a charge of 0.27 C
E = V
x Q = 1.5 V x 0.27 C = 0.405 J
6. A
bulb takes a current of 0.25 A. How many Coulombs per second? 0.25 C per second.
It
transfers 60W of power. How many Joules per second? 20
J per second
Calculate
the voltage of the supply. V = E ÷ Q = 20 ÷ 0.25 = 80 V
