Current
What is meant by electric current?
A: Rate of flow of electric charge.
State Ohm’s law.
A: The current is proportional to the potential difference across a conductor at constant temperature.
State the meaning of electrical power
The rate of electrical energy dissipated per time
State Kirchhoff’s first law.
A: The sum of currents entering a junction equals the sum leaving it.
How does current behave in a series circuit?
A: Same current flows through all components.
State the equation relating current, charge, and time.
I = Q/t
State equation of ohm's law
V = I x R
State the equation for electrical power.
P = V x I
State Kirchhoff’s second law.
A: The sum of emfs equals the sum of potential drops in a closed loop.
How does voltage behave in a parallel circuit?
A: Same voltage across each branch.
State the new equations of current (which shows the relation to charge of electron)
I = nAvq
Linear and pass through origin (constant gradient)
State unit of electrical power
Watt
At a junction, 5 A enters and two currents of 2 A and 1 A leave. What is the third outgoing current?
2 A leaves the junction
Two resistors of 4 Ω and 6 Ω are connected in series. Calculate the total resistance.
10 ohms
One coulomb of charge passes a point every 0.25 s. What is the current?
4 A
A resistor has a resistance of 5.0 Ω and carries a current of 2.0 A. Calculate the voltage across it.
A device operates at 6.0 V and draws a current of 0.50 A. Calculate the power.
3 watt
In a loop with a 12 V battery and voltage drops of 5 V and 3 V, what is the remaining voltage drop?
4 V
Two resistors of 6 Ω and 3 Ω are connected in parallel. Calculate the total resistance.
2 ohms
Wire B has double area and double density number of electron than wire A. Compare the current in wire A and B.
Wire B has current four times current in wire A
200 mA of current passes through 5.5 kohms of resistance. Calculate p.d across the resistance
1100 V
Derive from P = VxI and V = IxR, anothe equation for Power
P = V2/R or P=I2R
Explain why Kirchhoff’s laws are consistent with conservation of charge and energy.
A: First law → charge conservation; second law → energy conservation.
Two identical resistors are connected first in series and then in parallel to the same constant voltage supply. Compare the current drawn from the supply in the two arrangements.
Current in Parallel will be higher since the total resistance is lower