Primary and Secondary Voltages In A Transformer

In summary, the conversation discusses how to calculate the new output voltage of a transformer when the primary and secondary are reversed. Through the use of ratios and understanding the function of the transformer, the answer is determined to be 72V.
  • #1
scorpa
367
1
Hi!

I just got to my last homework question and am not quite sure how to figure it out, it goes like this:

Scott connects a transformer to a 24V source and measures 8.0V at the secondary. If the primary and secondary were reversed, what would the new output voltage be?

I'm not sure how to go about this. I know the basic ratios like

Np/ns = Vp/Vs = Is/Ip but I can't think of how to do this question. I'm sure it's super easy but I'm super dumb :grumpy:
Thanks for any help in advance! :biggrin:
 
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  • #2
Hint: If the transformer steps down the voltage when used one way, then what must it do if the primary and secondary are reversed?
 
  • #3
If they are reversed the voltage must step up, but I still don't see how to answer the question :(
 
  • #4
The input voltage doesn't change. It's still 24V.
 
  • #5
Would the new voltage be

24/8 = 8/x
x = 2.7V?
 
  • #6
Not even close. :smile: Remember: When used one way, the transformer steps down the voltage by a certain ratio (what is that factor?). So... when used in reverse, it will step up the voltage by the same factor.
 
  • #7
Um ok, so originally you have 24/8, and now we are stepping it up by that factor (3). So now we end up with the original 24v x 3 which equals 72v?
 
  • #8
Exactly right.

From Vp/Vs = Np/Ns, we know that Np/Ns = 3 for the original configuration. Now if we swap primary and secondary, Np/Ns = 1/3. Since the input voltage is still Vp = 24V, Vs = 72V.
 

1. What is the difference between primary and secondary voltages in a transformer?

Primary voltage refers to the input voltage that is supplied to the transformer, while secondary voltage refers to the output voltage that is produced by the transformer. Primary voltage is typically higher than the secondary voltage, and the relationship between them is determined by the transformer's turns ratio.

2. How are primary and secondary voltages related in a transformer?

The relationship between primary and secondary voltages in a transformer is determined by the transformer's turns ratio. This is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. For example, if a transformer has a turns ratio of 2:1, the secondary voltage will be half of the primary voltage.

3. Why is the primary voltage higher than the secondary voltage in a transformer?

The primary voltage is typically higher than the secondary voltage in a transformer due to the principle of energy conservation. In an ideal transformer, the power in the primary circuit is equal to the power in the secondary circuit. Therefore, since power is equal to voltage multiplied by current, a higher primary voltage results in a lower secondary voltage to maintain the power balance.

4. Can primary and secondary voltages be adjusted in a transformer?

Yes, the primary and secondary voltages in a transformer can be adjusted by changing the number of turns in the primary or secondary windings. This can be achieved by using a variable transformer or by physically changing the winding ratio. However, this is typically not done in practical applications as it can affect the efficiency and performance of the transformer.

5. How does the type of transformer affect the primary and secondary voltages?

The type of transformer can affect the primary and secondary voltages in several ways. For example, a step-up transformer will have a higher secondary voltage than the primary voltage, while a step-down transformer will have a lower secondary voltage. Additionally, the transformer's design and construction can also impact the primary and secondary voltages, such as in autotransformers where the primary and secondary circuits share a common winding.

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