MCQs: Component combinations
The internal resistace r in the following circuit is 1 Ω.
The pd from P to S is:
No current flows so pd across r is 0 V
Pd from P to S = 12 V
The current in the following circuit is 0.5 A.
The internal resistance r is:
Total resistance = V/I = 12/0.5 = 24 Ω
Internal resistance = 4 Ω
Each cell in the diagram below has an EMF = 6 V.
The current in the circuit is:
Total EMF = 6 - 6 + 6 = 6 V
I = V/R = 6/6 = 1 A
Note the following circuit.
The current is:
Total EMF = 12 +12 + 6 = 30 V
I = V/R = 30/12 = 2.5 A
Note the following combination of resistors.
The total resistance is:
The one in the middle draws no current (because there is no potential difference across it) so can be ignored.
Two 12 Ω in series = 24 Ω
Two 24 Ω in parallel = 12 Ω
Note the following combination of resistors.
The total resistance is:
R = 12 + 6
Note the following combination of resistors.
The total resistance is:
Two 12 Ω in parallel = 6 Ω
Total = 6 + 12 = 18 Ω
Note the following combination of resistors.
The total resistance is:
Total of each combination of 12 and 6 = 4 Ω (calculated using the resistors in parallel formula)
Two 4 Ω in parallel gives 2 Ω
Note the following combination of resistors.
The total resistance is:
1/R = 1/12 + 1/12 + 1/6 = (1 + 1 + 2)/12 = 4/12
R = 12/4
Note the following combination of resistors.
The total resistance is:
1/R = 1/R1 + 1/R2 = 1/6 + 1/12 = (2+1)/12 = 3/12
R = 12/3