P15 - Transformers

Question 1

transformer

Answer 1

A device used to change the value of alternating potential difference or current

Question 2

What does a step up transformer mean

Answer 2

increases size of alternating PD

Question 3

What does a step down transformer mean

Answer 3

decreases size of alternating PD

Question 4

What does a transformer consist of

Answer 4

-primary coil
-secondary coil
An iron core

Question 5

why is iron used

Answer 5

easily magnetised /demagnetised

Question 6

primary coil

Answer 6

Where the alternating current is supplied to

Question 7

secondary coil

Answer 7

where there is a changing magnetic field as a result of the iron core becoming magnetised

Question 8

why is alternating pd induced

Answer 8

Alternating current supplied to primary coil
- the current is continuously changing direction so there is a magnetic fetid around primary coil.
- iron core easily magnetised so current passes through
- now due to iron core transferring the magnetism their is now a magnetic field inside of the secondary coil also inducing P.D
- if secondary coil part of the complete circuit then alternating current will flow .

Question 9

if secondary coil is attached to bulb in a complete circuit

Answer 9

• induced pd
  = ac so bulb lights up

Question 10

energy is transferred from

Answer 10

primary to secondary
-despite not being electrically connected

Question 11

Why is no P.D produced from direct current

Answer 11

only works with ac
Since their is no changing magnetic field around the secondary coil so no induced P.D

Question 12

What are the coils like in a step up transformer

Answer 12

more turns in secondary than primary

Question 13

In a step down transformer what are the proportion of coil

Answer 13

• more in primary than secondary

Question 14

formula for Vp/Vs =

Answer 14

Np/Ns

Question 15

Using the equation if their is 50 volts across primary coil and 200 volts on secondary and their gngibgbuis 3 coils on the primary how many coils in the secondary coil

Answer 15

12

Question 16

if 100% efficient formula

Answer 16

P PD x P I = S PD x S I

Question 17

step up transformer - pd

Answer 17

pd is raised
-current is lowered

Question 18

why is current lowered

Answer 18

heating effect is smaller
-less power is wasted

Question 19

if pd increases and current decreases

Answer 19

same amount of power
-less wasted due to heating effect
-more efficient

Question 20

heating effect is directly proportional to

Answer 20

I^2
current ^2