summary of physics chapter 7 electric and magnetic of icse
Answers
Answer:
A magnet is a material or object that produces a magnetic field that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets. Understand the definition of magnets and how they work, and explore the Earth's magnetic field.
Explanation:
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ICSE Physics Class 7 Notes Chapter 7 Electricity and Magnetism
→ Some materials behave in a particular manner showing magnetic properties.
→ A freely suspended bar magnet always point in North-South direction.
→ Like poles repel each other while unlike poles attract each other.
→ Magnet is neutral at its centre and has maximum magnetic effects at its ends called the poles.
→ Poles always exist in pairs with opposite polarities and can never be isolated.
→ Examples of magnetic substances are iron, cobalt, nickel.
→ Examples of non-magnetic substances are wood, plastic aluminium, copper.
→ The poles are not exactly the ends of the magnet but they are slightly inside.
→ For a given magnet, both the poles are of equal strength.
→ Earth’s magnet has its south pole situated near the geographic north.
→ Electromagnets are the temporary magnets which are made up of soft iron core with a winding of insulated copper wire.
→ Freely suspended current carrying solenoid always rests in north-south direction.
→ A direct current source has the fixed positive and negative terminals, e.g. a battery.
→ Hans Christian Oersted discovered that if an electric current is passed through a conductor, a magnetic field is
developed around it.
→ The study of magnetic effects produced due to electric current is known as electromagnetism.
→ The direction of magnetic field due to a straight current carrying conductor is obtained by any of the following rules:
(a) Right Hand Thumb Rule.
(b) Right Hand Cork Screw Rule.
→ The property due to which a changing magnetic field within a closed conducting coil induces electric current in the coil is called electromagnetic induction.
→ The current produced in a closed coil when magnetic lines of force rapidly change within it is called the induced current.
→ The symbol for alternating current is –
→ The strength of induced current can be increased by increasing the –
(a) the number of turns in the coil
(b) strength of the magnet used
(c) relative speed between the magnet and closed coil.
→ We cannot think of modern life without electricity. We light our homes and other places of work with electricity.
→ It is used to run electric fans, televisions, geyser, electric irons, room heaters, refrigerators, music system etc.
→ Cell is a primary source of electricity. A combination of two or more cells is a battery.
→Some other sources of electricity are generator and solar cells.
→ The path along which an electric current flows is called a circuit.
→ Electricity has the following effects :
(a) Heating effect
(b) Magnetic effect
(c) Chemical effect
(d) Mechanical effect
→ When an electric path is complete is called closed circuit and the path with a break is called open circuit.
→ The substances which allow the electricity to flow through them are called conductors, e.g. metals, human body etc.
→ The substances which do not allow electricity to flow through them are called insulators, e.g. wood, paper, glass etc.
→ The consumption of electricity is calculated from the meter in kWh.
→ Electric fuse is a device which limits the current in an electric circuit.
→ All electrical appliances are connected in parallel in household circuits.
→ We should be cautious in using electricity.
→ Certain precautions should be taken before working on an electrical gadget or circuit.