Transformers in Series, calculating the current

[joshb]

I have been given the attached question by my mentor.

I have used the standard transformer equations (Vs/Vp=Ns/Np etc.) but I am struggling to work toward the right answer. I am using 4 amps for question A (standard ohms law) but don't think I am tackling this right. As for current in the primary I always seem to come up with 1.6 amps. My mentor has told me this is wrong and I should be looking at the two unknowns. I'm completey stuck!

Can anyone help?

 

[joshb]

Sorry, this is the question.

https://www.physicsforums.com/attachment.php?attachmentid=7516&stc=1&d=1155649799"

 

[piercas]

I understand your frustration and confusion with this problem. It can be challenging to wrap your head around complex equations and unknown variables. However, I can provide some guidance to help you approach this problem more effectively.

First, it's important to understand the concept of transformers in series. When transformers are connected in series, the secondary winding of one transformer is connected to the primary winding of the next transformer, creating a chain-like structure. This leads to a cumulative effect on the voltage and current, where the output voltage is the sum of the individual transformer voltages and the output current is the same as the input current.

Now, let's look at the equations you mentioned. The equation Vs/Vp=Ns/Np is known as the turns ratio equation, where Vs and Vp are the secondary and primary voltages, and Ns and Np are the number of turns in the secondary and primary windings, respectively. This equation is used to calculate the output voltage of a transformer.

However, to calculate the current in a series of transformers, we need to use the current ratio equation, which is Is/Ip=Np/Ns. Here, Is and Ip are the secondary and primary currents, and Np and Ns are the number of turns in the primary and secondary windings, respectively. This equation tells us that the current in the secondary winding is inversely proportional to the number of turns in the secondary winding.

Now, let's apply this equation to the problem you have been given. You mentioned that you are using 4 amps for question A, which I assume is the secondary current. To find the primary current, we need to know the number of turns in the primary winding. This is where the "two unknowns" that your mentor mentioned come into play. You need to find a way to determine the number of turns in the primary winding based on the information given in the question.

One approach could be to use the power equation, P=IV, where P is power, I is current, and V is voltage. Since the transformers are in series, the input power will be equal to the output power. This means that you can equate the input voltage (Vp) times the input current (Ip) to the output voltage (Vs) times the output current (Is). This will give you a relationship between Vp and Ip, which you can use to solve for Ip.

Another approach could be to use the concept of conservation