Potential difference and ohms law

This is because in series, the voltage is split between the bulbs, but in parallel, they each get the full voltage.In summary, a 3 Ohm and a 1.5 Ohm resistor are wired in parallel and the combination is wired in series to a 4 Ohm resistor and a 10 V emf device. The total resistance is 5 Ohms and the total current is 2 amps. The voltage drop over the 4 Ohm resistor is 8V and the remaining voltage is 2V. The voltage remains the same in each path when dealing with parallel circuits.
  • #1
nautica
A 3Ohm and a 1.5 ohm resistor are wired in paralles and the combination is wired in series to a 4 ohm resistor and a 10 V emf device. The potential difference on across the 3 ohm resistor is?

I reduced the 2 in parrallel to 1.875 ohms and then addes the 4 ohm, which gave me a total resistance of 5.875 ohms. Then measured the current using ohms law, which gave me 1.7 amps. Then multiplied that times the 3 ohms to get 5.1 V.

But that is not one of the answer choices, where did I go wrong.

these are the choices: 2V,6V,8V,10V,12V

Thanks
Nautica
 
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  • #2
Wouldn't the equivalent resistance be 1? making the total resistance 5 ohms? Then you'd have a (10/5)*1 volt drop across the 2 resistors in parallel and a (10/5)*4 volt drop across the 4 ohm resistor.

Look at the resistors in parallel again:

[tex] R_{eq} = \left(\frac 1 3 + \frac 1 {1.5} \right)^{-1} = \left(\frac{1+2}{3}\right)^{-1} = 1 [/tex]
 
  • #3
nice, maybe I need to go back to 3rd grade math.
 
  • #4
I am still not coming up with the answer.

If the total resistance is the 1 ohm, which i reduced, plus the 4 ohm in series. That gives me a total resistance of 5 ohms. Then I plug that into ohms law, which is V=IR and it gives me a total current of 2 amps.

To find the potential difference on the 3 ohm, I would have to cut the current in half, which is 1 and then use ohms law, which is V=IR so 1 x 3, which gives me 3, but that is wrong.

Nautica
 
  • #5
Originally posted by nautica
A 3Ohm and a 1.5 ohm resistor are wired in paralles and the combination is wired in series to a 4 ohm resistor and a 10 V emf device. The potential difference on across the 3 ohm resistor is?

I'm getting the answer as being 2V


Resistance of parallel things

[tex]R = (3^-^1 + 1.5^-^1)^-^1[/tex]

[tex]R = 1 \Omega[/tex]

resistance total

R = 1 + 4
R = 5[tex]\Omega[/tex]

total current:

[tex]I = \frac{V}{R}[/tex]

[tex]I = \frac{10}{5}[/tex]

I = 2A

voltage drop over the 4[tex]\Omega[/tex] resistor:
V = IR
V = (2)(4)
V = 8V

voltage remaining:
V = 10 - 8
V = 2V
 
  • #6
So how is that split between the remaining 3 and 1.5 ohm on the parrallel
 
  • #7
It isn't. When dealing with a parallel, the voltage is the same in each path. That's why hooking lightbulbs in parallel makes power consumption much higher than hooking them in series.
 

What is potential difference?

Potential difference, also known as voltage, is the difference in electric potential between two points in an electric circuit. It is measured in volts (V) and is the driving force that causes electric current to flow.

What is Ohm's Law?

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. This means that as the potential difference increases, the current also increases, and vice versa. Mathematically, it can be expressed as I = V/R, where I is the current in amperes (A), V is the potential difference in volts (V), and R is the resistance in ohms (Ω).

How is potential difference measured?

Potential difference can be measured using a voltmeter, which is a device that is connected in parallel to the circuit and measures the voltage between two points. It can also be calculated using Ohm's Law, by measuring the current and resistance in the circuit.

What is resistance?

Resistance is the measure of how much a material or component opposes the flow of electric current. It is measured in ohms (Ω) and is dependent on the material, length, and cross-sectional area of a conductor. The higher the resistance, the lower the current for a given potential difference.

How does resistance affect potential difference?

According to Ohm's Law, potential difference is directly proportional to resistance. This means that as resistance increases, the potential difference also increases, and vice versa. A higher resistance in a circuit will result in a lower current for a given potential difference.

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