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

y10 Mock Exam

Answer ALL questions

Some questions must be answered with a cross in a box ( ). If you change your mind about an answer, put a line through the box ( )and then mark your new answer with a cross .

1 Using the Sun

(a) A student uses a converging lens to make an image of the Sun.

R to the right of P and on the dotted line

 (i) Complete the sentence by putting a cross ( ) in the box next to your answer.

The lens forms a real image of the Sun at P, where the light rays cross.

The distance d is the                                                                                                               (1)

ÿ       A focal point

ÿ       B focal lengthþ

ÿ       C object length

ÿ       D object distance

(ii) Radiation from the Sun includes some infrared waves. The lens bends infrared waves less than it does ordinary light.

Label, with an R, a place on the diagram where the infrared rays could cross.                               (1)

(d) The Electromagnetic spectrum.                                                   

(i) Fill in the missing waves in the Electromagnetic spectrum                                                          (1)

 All three needed for 1 mark

Radio-waves

Microwave

Infra red

Visible light

Ultra violet

x-rays

Gamma rays

increasing frequency -------------------------------------------------------------------------->

 

(ii) Draw a labelled arrow under the diagram to show increasing frequency.                                (1)

(c) In some countries, infrared rays from the Sun are used to cook food. Light and infrared rays are both focused using a converging mirror.

(i) State what happens to the rays at S.                                                                                 (1)       

…The rays are reflected 

(ii) Explain why the light rays and infrared rays converge towards the same point.                                    (2)

Both types of rays must obey the law of reflection, as the angles of incidence are the same for both types of ray, so are the angles of reflection. They are therefore brought to a focus at the same point

(iii) The infrared waves travel at a speed of 300 000 km/s. They take 500 s to travel from the Sun to the Earth. Calculate the distance between the Earth and the Sun.                                                        (3)

Velocity (v) = Distance (d) /time (t)

Rearranging d = v x t      v = 300 000 km/s           t = 500s

            d = 300 000 x 500

            d = 150 000 000 km

note only 2 marks possible without the workings

distance = 150 000 000. km

 (Total for Question 1 = 10 marks)

2 Galaxies and the Universe

A scientist is observing the light waves emitted from a distant galaxy.

(a) Which of these statements is not true for light waves?

Put a cross ( ) in the box next to your answer.                                                                                (1)

ÿ       A light waves transfer matter x

ÿ       B light waves transfer energy

ÿ       C light waves can transfer information

ÿ       D light waves are a type of electromagnetic radiation

(b) The light detected by the scientist has a wavelength of 6.56 x 10^-7 m and a frequency of 4.57 x 10¹⁷Hz.

Calculate the speed of light.

Use your formula sheet                                  Show all your working                                              (2)

V= fλ               f = 4.57 x 10¹⁷ Hz         λ = 6.56 x 10^-7 m

V = (4.57 x 10¹⁷) (6.56 x 10^-7)

V = 3 x 10¹¹ m/s

(This is not the speed of light which is 3 x 10⁸ m/s. The question correctly states the wavelength of visible light. You can work out the correct frequency for yourself)

Wave speed =             3 x 10¹¹                        m/s

(c) A galaxy is a collection of stars. Stars with a similar mass to our Sun will evolve to become red giants, before finally becoming white dwarfs at the end of their life.

What will stars with a mass greater than the Sun become at the end of their life?                                    (2)

The end state of a star with a greater mass than the sun is either a neutron star or a black hole

(d) The Big Bang theory is the currently accepted theory of how the Universe started.

Described how the Universe began according to this theory.                                                           (1)

The whole of the current universe (space, matter, energy and time) was compressed into a point of almost zero volume. It has since expanded into the universe we observe today.

*(e) Red-shift and cosmic microwave background radiation are both strong pieces of evidence in support of the Big Bang theory.

Explain how the evidence of red-shift and cosmic microwave background radiation have led to the Big Bang theory being the currently accepted theory of how the Universe began.

                                    (6)

REDSHIFT

The theory of the big bang predicts that the universe must be expanding.

All galaxy clusters show a redshift. This means they are travelling away from us.

The further the distance to the galaxy cluster the greater the redshift.

This tells us that the velocity of these galaxy clusters increases with distance from us.

This evidence fits in with an expanding universe

COSMIC MICROWAVE BACKGROUND RADIATION

The big bang theory predicts the early universe was very hot and very dense. There should be energy left over from this time.

The CMBR is a microwave signal that comes from space. It is the same in all directions. The signal is the energy from the hot young universe. As the universe has expanded the wavelength of these electromagnetic waves has been stretched so they now lie in the microwave band.

The redshift of the galaxies and the CMBR are both predicted by the big bang theory. This is why it is generally accepted

(Total for Question 2 = 12 marks)