Higher
Question
- Calculate the total resistance of the circuit.
- Calculate the current flowing in the \({3}\Omega\) resistor.
- Calculate the voltage across the \({8}\Omega\) resistor.
- Calculate the current flowing in the \({6}\Omega\) resistor.
1. First calculate the parallel resistance:
\(\frac{1}{R}=\frac{1}{R}_{1} +\frac{1}{R}_{2}\)
R1 = \({8}\Omega\)
R2 = \({6}\Omega\)
\(\frac{1}{R}=\frac{1}{8} +\frac{1}{6}\)
\(\frac{1}{R}=\frac{7}{24}\)
R = \(\frac{24}{7}\)
R = \({3.43}\Omega\)
This is in series with the \({3}\Omega\). The total resistance R is given by:
R = R1 + R2
R = \({3}\Omega + {3.43}\Omega\)
R = \({6.43}\Omega\)
The total resistance of the circuit is \({6.43}\Omega\).
2. The circuit above has now been simplified to:
Hence, the voltage across the \({6.43}\Omega\) resistor is 12 V.
I = \(\frac{V}{R}\)
V = 12 V
R = \({6.43}\Omega\)
I = \(\frac{12 V}{{6.43}\Omega}\)
I = 1.87 A
The current is the same in all parts of a series circuit and so this is the current through the \({3}\Omega\) resistor too.
The current flowing in the \({3}\Omega\) is 1.87 A.
3. The current through the \({8}\Omega\) resistor is not known so we cannot use V = IR to calculate the voltage across it directly.
However, we do know the current through the \({3}\Omega\) resistor, so we can calculate the voltage across it.
V = IR
I = 1.87 A
R = \({3}\Omega\)
V = 1.87 A x \({3}\Omega\)
V = 5.61 V
The total voltage = 12 V
Hence, the voltage across the two parallel resistors = 12 V 鈥 5.61 V = 6.39 V.
The voltage across each parallel resistor is the same.
Hence, the voltage across the \({8}\Omega\) = 6.39 V.
The voltage across the 8惟 resistor is 6.39 V.
4. The voltage across each parallel resistor is the same.
Hence, the voltage across the \({6}\Omega\) resistor = 6.39 V.
I = \(\frac{V}{R}\)
V = 6.39 V
R = \({6}\Omega\)
I = \(\frac{6.39 V}{{6}\Omega}\)
I = 1.07 A
The current through the \({6}\Omega\) is 1.07 A.