Week 4 and 5 – SS1 Third Term Physics Notes

WEEK 4
TOPIC: SAFETY DEVICE – FUSE
CONTENT : Fuse

Types of Fuse
Detecting Fault in a Circuit
Fuse
Fuse is a protective device, designed to melt at the passage of excess electric current through it. It can also be defined as a device for opening circuit, by means of a conductor designed to melt when an excessive current flows along it. The conductor actually designed to melt is called fuse element.
Fuse element is the part of the fuse that is designed to melt and then open the cct
Current rating of a fuse : it is the minimum current which the fuse will carry for an indefinite/ unlimited period without deterioration of the fuse element
Fusing current: is the minimum current that will cause the fuse element to heat up and melt/ rapture or blow.
Fusing factor is the ratio of the fusing current upon the current rating.
Fusing factor = fusing current/ current rating

 EVALUATION

1. Define the following terms (a) fuse (b) fuse element (c) current rating of a fuse
2. State the relationship between fusing factor, fusing rating and current rating
   

Types of Fuse

• Re-wire able fuse
• Cartridge fuse
• High breaker capacity fuse
• Others

Detecting Fault in Electric Circuit

• Merger tester – insulation resistance test
• Test bell – polarity test
• Earth-loop impudence tester – test for earthling
• Continuity tester – test for continuity

EVALUATION

1. List three types of fuse
2. Mention four ways of detecting fault in an electric circuit

Reading Assignment : Read more on safety devices – New school physics (pg 83-84)

 
WEEKEND ASSIGNMENT

1. Fuse is a protective device, design to ……….. (a) stick (b) melt (c) disappear (d) repel
2. The conductor designed to melt is called ……. (a) fuse element (b) fuse (c) resistor (d) cartridge fuse
3. The following are examples of fuse except ……. fuse (a) re-wire able (b) merger (c) cartridge (d) high breaking capacity
4. Which of the following correctly gives the relationship between linear speed v & angular velocity w of a body moving uniformly (a) v=w r (b) v=w²r (c) v=wr² (d) v=w/r
5. The motion of the prongs of a sounding turning fork is (a) random (b) translational (c) rotational (d) vibratory

THEORY

1. Define the following terms (a) fuse (b) fuse element (c) current rating of a fuse
2. Mention four ways of detecting fault in an electric circuit

  WEEK 5
TOPIC: MATTER, ATOMIC STRUCTURE, STATES OF MATTER,
DIFFUSION, OSMOSIS, BROWNIAN MOTION
CONTENT : Atomic Structure
Molecular Theory of Matter
Diffusion and Osmosis
Matter
Matter is defined as anything that has mass and occupies space. All substances are made up of matter. It exists in three states namely, solid liquid and gas. Examples of solids are ice, brick, metal, concrete, wood etc. examples of liquid are water, milk, oil etc while that of gas are oxygen, nitrogen, CO₂
Structure of Matter
Matter is made up of discrete particles namely atom, molecules and ion.

• Atom: An atom is the smallest particle of an element which can have a separate existence. Atom is made up of a nucleus and a revolving electron around an orbit or shell. The nucleus consists of proton and neutron. The proton is positively charge, electron is negatively charge and neutron is neutral (i.e. has no charge). The number of protons equates the number of electrons.An atom that contains the same number of protons and electrons is said to be electrically neutral.

• Molecule: A molecule is a group of atoms of the same or different elements joined in simple proportion. They come together to make up matter

Brownian Motion

• Molecules exist
• Molecules are continually in motion

EVALUATION

1. Explain the structure of matter
2. What is the importance of Brownie’s motion

 
Molecular Theory of Matter
Using kinetic theory explain the (i) definite structure of solid (ii) shape of liquid (iii) gas

1. Solid: Matter consists of molecules which are tightly held together by intermolecular forces to make the molecules to vibrate about their mean positions, giving the solid definite shape. If the solid is heated, the total energy is divided among the molecules to make them vibrate faster. Eventually, they move so fast that they break loose from their fixed position.
2. Liquid: The molecules of a liquid can move about within the given volume of the container. Hence, liquid has its own size but no shape. If the liquid is heated, its molecules gain kinetic energy and move faster, until eventually molecules can escape from the surface. The liquid then vanishes and turns to gaseous state.
3. Gas: The molecules of a gas are also in constant motion like the liquid but comparatively far apart. They move at high speed, colliding with one another and with the walls of their containing vessel. They fill the vessel and exert pressure on the walls of the container. The pressure of the gas is caused by the collision of the molecules with the walls of the container.

Diffusion and Osmosis

Diffusion: Diffusion is the process by which different forms of matter (fluids) mix intimately with one another owing to the kinetic nature of their molecules. It is also the tendency of a gas to mix with another and fill an empty space as a result of the constant random motion of the molecules.

 
 
 
 
 
 
 The rates of diffusion or factors affecting diffusion are (i) density (ii) mass (iii) temperature (iv) pressure (v) concentration
Also, Graham’s law of diffusion states that at constant temperature, gas diffuse at rates inversely proportional to the square root of their vapour densities.
R α1/√M → R = K/√M .;K = R√M
Hence, R1√M1 = R2√M2 = …= Rn√Mn
Hence, R1/R2 = √M2/√M1    where R – rate of diffusion, M – relative molecular mass. NB : (i) R = volume (gas)/time
(ii) Relative molecular mass is twice its vapour density
Osmosis: This is the movement of water molecules from the region of higher concentration to a region of lower concentration through a semi-permeable membrane.
EVALUATION
1.    Using kinetic theory, explain the definite structure of solid
2.    State four factors that affect the rate of diffusion
Reading Assignment : Read more on atomic structure, diffusion and osmosis – New school physics (pg 87-92)

WEEKEND ASSIGNMENT
1.    The following are examples of theory except (a)concrete (b) oil
(c) brick (d) metal
2.    The nucleus of an atom consist of (a) proton and electron (b) neutron and
electron (c) proton and neutron (d) none of the above
3.    Positive ions are called ____ (a) camions (b) anions (c) molecules
(d) atom
4.    When is atom said to be electrically neutral (a) when the number of proton
equals the number of neutron (b) when the number of protons equals the
the number of electrons (c) when the number of proton is greater then the
number of electron (d) when the number of neutron equals the number of
electron
5.    ion is a form of ____ (a) atom (b) molecules (c) matter
(d) none of the above.
THEORY
1.    Using kinetic theory, explain the definite structure of solid
2.    State four factors that affect the rate of diffusion