Rearranging formulae

Tranformers Worksheet with answers

Transformer Effect 

 

V_in = N_p             or         V_out = N_s

V_out     N_s                            V_in         N_p

 

1. A step down transformer reduces voltage from 240 V (V_in) to 6 V.  If there are 1000 turns on the primary windings (N_p),  how many are there on the secondary windings ?

V_out = N_s               6V/240V = N_s/1000   N_s/1000 = 0.025      N_s = 1000 x 0.025 = 25 turns

 V_in         N_p

 

 

2. A step down transformer reduces voltage from 240 V (V_in) to 12 V (V_out).  If N_p = 200 turns calculate  N_s.

 

V_out = N_s            12V/240v = Ns/200 Ns = 12/240 x 200 = 10 turns

V_in         N_p

 

 

 

3. A transformer has 1000 turns on it’s primary windings and 100 in the secondary . If V_in is in 20V calculate V_out.

 

V_out = N_s            V _out/20v = 100/1000  V_out= 20 (100/1000) = 2 V

V_in         N_p

 

4.  In a transformer N_p = 2000 turns and N_s = 50 turns.  If V_in =400 V, calculate V_out.

V_out = N_s            V _out/400v = 50/2000  V_out= 400 (50/2000) = 10 V

V_in         N_p

 

5.  A step up transformer increases voltage from 4 V to 40 V.  If N_p = 100 turns calculate N_s.

V_out = N_s            40V/4v = Ns/100 Ns = 40/4 x 200 = 2000 turns

V_in         N_p

 

6.  A step down transformer reduces voltage from 100 V to 10 V.  If N_p = 2000 turns calculate N_s.

V_out = N_s            10V/100v = Ns/20000 Ns = 10/100 x 200 = 20 turns

V_in         N_p

 

7.  In a transformer N_s = 10 turns and N_p = 500 turns.  If V_out = 10 V calculate V_in.

            V_in/V_out = N_p/N_s rearranging V_in = V_outN_p/N_s  V_in = 10(500/10) = 500V

 

8.  If N_s = 40 turns and Np = 4000 turns calculate V_in if V_out = 10 V.

 

V_in/V_out = N_p/N_s rearranging V_in = V_outN_p/N_s  V_in = 10(4000/40) = 1000V

 

 

 

 

 

Detecting Epicentre of an Earthquake

Revision session

Mock Mark Scheme

Universe revision

Universe

1.            Our Solar System may have formed from the remains of a large star.

(a) Suggest how the Sun was formed. (3)

                b)            What changes to our Sun are likely to take place in the future?  (4)

2.            The Big Bang theory attempts to explain the origin and possible future of the Universe.

(a) Describe the main features of the Big Bang theory.  (3)

                (b)          State two pieces of evidence that support the Big Bang theory.  (2)

3.                      The Big Bang theory and the Steady State theory are both about the beginning and possible future of the Universe.

(a) (i)            Explain the main differences between the two theories.
Refer to the origin and likely future of the Universe in your answer.(4)

(b) Give 2 pieces of evidence that are not predicted by the Steady State theory that can be accounted for by the Big Bang Theory.  (4)

 4.           The graph shows how the recessional speed of five galaxies varies with distance from the Earth.

(a) Describe the general pattern shown by the graph (on the previous page) for how the recessional speed changes with distance from the Earth (1)

(b) Explain how the measurements support Hubble’s idea of the ‘Big Bang’ theory of the origin of the Universe.  (2)

(d) What would be the distance to a galaxy having a recessional speed of 30 000 km/s? (2)

5.                 (a) A star like the Sun forms when large clouds of hydrogen, helium and dust are attracted together by the force of gravity. What is the name of the object formed before the sun became a star.        (1)

                (b)  How does a star produce energy?    (2)

                (c) Scientists believe that the Sun will eventually become a white dwarf.

                                Outline the possible fates of much larger stars. (5)

 

Refraction