Help with this confusing circuit test tmrw Find i across resistor.

In summary, the circuit problem involves finding the current across a resistor. To solve it, the 12 Ohm resistor can be ignored as it has no effect on the rest of the circuit. The voltage across the 40 Ohm resistor can be found by calculating the equivalent resistance of the parallel resistors (60, 40, and 48 Ohm) and using a voltage divider with the 8 Ohm and 16 Ohm resistors. The resulting current through the 40 Ohm resistor is 4A.
  • #1
nchin
172
0
Help with this confusing circuit! test tmrw! Find i across resistor.

http://imageshack.us/photo/my-images/202/circuitu.jpg/

my teacher lectures to fast and i don't understand the notes i put down. can someone explain this one to me please??
 
Physics news on Phys.org
  • #2


This is the way I would approach the problem...

You can ignore the 12 Ohm resistor because it's across the 240V supply and has no effect on the current or voltage in the rest of the circuit.

To find the current in the 40 Ohm I would first aim to work out the voltage across it.

I note that the 60, 40 and 48 Ohm are in parallel and that 60//40//48 works out as ...

1/(1/60 + 1/40 + 1/48) = 16 Ohm

Then I note that the 8 Ohm and 16 Ohm form a voltage (aka potential) divider...

http://en.wikipedia.org/wiki/Voltage_divider

So the required voltage across the 40 Ohm is...

240 * 16/(8+16) = 160V

Therefore the current through the 40 Ohm is

I40 = 160/40 = 4A
 

FAQ: Help with this confusing circuit test tmrw Find i across resistor.

What is the purpose of this circuit test?

The purpose of this circuit test is to determine the current (i) across a resistor in a given circuit. This information is important in understanding the behavior and characteristics of the circuit.

How do I find the current across the resistor?

To find the current (i) across the resistor, you can use Ohm's Law which states that current is equal to the voltage (V) divided by the resistance (R). In this case, you will need to measure the voltage and resistance values of the circuit to calculate the current.

What if I don't have the voltage and resistance values?

If you do not have the voltage and resistance values of the circuit, you can still find the current by using a multimeter. Set the multimeter to measure current and place it in series with the resistor. The reading on the multimeter will be the current across the resistor.

Can I use Kirchhoff's Laws to find the current?

Yes, you can use Kirchhoff's Laws (specifically the Kirchhoff's Current Law) to find the current across the resistor. This law states that the sum of currents entering a node is equal to the sum of currents leaving the node. By applying this law to the circuit, you can solve for the current across the resistor.

What are some common mistakes to avoid when finding the current?

Some common mistakes to avoid when finding the current across a resistor include using the wrong units (e.g. using volts instead of millivolts), not accounting for the direction of current flow, and not properly connecting the multimeter in series with the resistor. It is important to double check your calculations and measurements to ensure accuracy.

Similar threads

How to Calculate the Complex Op Amp in Circuit Diagram
Replies
8
Views
2K
Comp Sci Need help finding the resistor size for a circuit (Ohm's law)
Replies
1
Views
1K
Engineering Find di(0+)/dt and dv(0+)/dt of circuit containing resistor, inductor
Replies
3
Views
2K
Engineering Unknown resistor in a series-parallel circuit
Replies
17
Views
10K
Engineering Why Is Nodal Analysis Confusing in This Circuit Example?
Replies
7
Views
1K
Engineering Simplifying a series / parallel circuit and calculating unknown values
Replies
3
Views
2K
Engineering Can a voltage test source help solve for Rth in a complex Thevenin's circuit?
Replies
10
Views
1K
Engineering Norton/Thevenin Equivalent circuits with a dependent voltage source
Replies
9
Views
4K
Engineering How to Calculate Thevenin Equivalent Circuit
Replies
5
Views
2K
Engineering How do short/open-circuit tests work for step-up transformers?
Replies
7
Views
2K

Hot Threads

Recent Insights

Back
Top