PAG 11.1 Investigating Transformers Flashcards
What is the difference between a step-up and step-down transformer?
Step up transformers have a greater voltage across their secondary coil, whereas step-down transformers have a greater voltage across their primary coil.
What is the benefit of using laminated cores in the transformer?
The addition of lamination layers reduces the eddy currents in the core. This improves the efficiency of the transformer since less energy is wasted
What is the benefit of using a magnetically soft for the transformer core
Magnetically soft materials can be easily magnetised and demagnetised.
This will improve the efficiency of the transformer, since less energy will be wasted in magnetising and demagnetising the core
How can the power input of your transformer be calculated?
The power input will equal the product of the input current and input voltage
Why will the efficiency of your transformer not be 100%
Energy will be dissipated to the surroundings due to eddy currents in the core and the heating of the coils in the wire
How can the energy losses in the coils of the wire be reduced?
Resistance of the wire reduced by using thick copper wire.
Coil heats up less, and therefore less energy being wasted
What does Faraday’s law state?
An induced EMF will be directly proportional to the rate of change of the flux linkage
What is an AC power supply?
A supply whose current is continually changing direction. This usually occurs at a set frequency.
Why must an AC supply be used in this experiment?
For EMF to be induced, there must be a constantly changing magnetic field since there needs to be a rate of change of flux linkage.
This is only achieved if the current is continually changing directions
How do you calculate the turn ratio of a transformer?
Divide the number of turns on the secondary coil by the number of turns on the primary coil
What is the relationship between turn ratio and voltage ratio in an ideal transformer?
Turns Ratio = N_s / N_p = Voltage Ratio = V_s / V_p
What is the relationship between the turn ratio and current ratio for an ideal transformer?
the current ratio is the inverse of the turn ratio
How is a magnetic field set up in the core of a transformer?
When a current flows through a wire, a magnetic field is induced around it.
When current flows through the primary coil, the core becomes magnetised.
What could you add to your circuit set-up to allow the current to be varied?
A rheostat to allow the current inputted into the primary coil to be varied.
What safety precautions should be taken in this experiment?
Input voltage should be sufficiently low to ensure output voltage is of a safe level, even with a greater number of turns on secondary coil.
The power supply should be switched off when not in use to avoid the apparatus becoming too hot.
