Electric Current (SS) gceo physics

The electric charges in motion is called electric current and it forms the basis of current electricity. Static electricity, or electrostatics, on the other hand involves charges at rest.

Electric current (I) is the rate of flow of charges.(Q)

• SI unit: Ampere (A)
• Can be measured by an ammeter (must be connected in SERIES to the circuit)

I=Qt

A current of one ampere is a flow of charge at the rate of one coulomb per second.

For electric current in a metal conductor (a solid), the charge carriers are electrons. For historical reasons, the direction of the conventional current is always treated as the opposite direction in which electron effectively moves.

• Current in gases and liquid generally consists of a flow of positive ions in one direction together with a flow of negative ions in the opposite direction.

Electric current generates a magnetic field. The strength of the magnetic field depends on the magnitude of the electric current.

Current electricity consists of any movement of electric charge carriers, such as subatomic charged particles (e.g. electrons having negative charge, protons having positive charge), ions (atoms that have lost or gained one or more electrons), or holes (electron deficiencies that may be thought of as positive particles)

• If the direction of the current (charge flow) is fixed, it is known as a direct current. If the motion of the electric charges is periodically reversed; it is called an alternating current.
• Analogy to river:

In order to help you understand the concept of current better, you can think of a river. Current in an electric circuit is similar to water flowing through the river.

Propagation Of Sound Waves Gceo level

Tuning Fork

Vibration in the tuning fork produces disturbances in the surrounding air. When the prongs’ movement is outwards, the prongs push the surrounding air molecules away, creating a local compression.

This disturbance of air layers is then passed from molecule to molecule by collisions, causing the local compression to move outwardly.

When the prongs’ movement is inwards, a partial void, or rarefaction is created. Pressure differences causes the air molecules to rush back into the region again. This periodic to-and-fro movement of the prongs will create alternating regions of compressions and rarefactions. The sound waves span outwardly parallel to the direction of the wave propagation (longitudinal nature).

• In air, compressions are regions where the pressure is higher than surrounding air and rarefactions are regions where pressure is lower than the surrounding air.

Notes:

• The energy of the sound waves is propagated and carried by colliding particles of a material medium. Hence, a (material) medium is required in order to transmit these (energy) waves.
• The speed of energy propagation is dependent on the proximity of these particles in a medium. Hence, given that the proximity of particles in the air, liquids or solids is different, the speed of sound differs in air, liquids and solids. Sound travels faster in denser media. It travels faster in liquids than in gases and fastest in solids.

Gceo level Physics Sound

Sound is a mechanical wave phenomenon and is normally associated with our sense of hearing. Sound is a property of vibrating objects.

• Sound is produced by vibrating sources in a material medium. Medium can be any gas, liquid or solid.
• The vibrating sources set the particles of a medium in vibration in such a way that sound travels outwards in the form of longitudinal waves.
• Some of the energy of the vibrations are transmitted over a distance.

Examples of vibrating sources:

• Musical instruments, like drums, guitar
• Hitting a piece of iron with a hammer
• Loudspeakers (Consists of a cone which vibrates under the effects of electricity and magnetism)
• Explosion resulting from explosives.

Physics speed notes gceo level

Speed is the distance moved per unit time.

• SI unit is metre per second (ms−1)
• Scalar quantity
• Equation: Speed=dt, where d is distance travelled and t is time taken
• Average speed can be calculated using totaldistancetravelledtotaltimetaken
• Instantaneous speed is the speed at any instant
  1. Measured by a speedometer

A speedometer measures the instantaneous speed

Velocity (v) of an object is the rate of change of displacement with respect to time.

• SI unit is metre per second (ms−1)
• Vector quantity
• The magnitude of velocity is speed
• v=st, where s is displacement and t is time taken

As velocity is a vector quantity, you have to specify its magnitude and direction to completely describe it.

THE WORLD POPULATION AND THE TOP TEN COUNTRIES WITH THE HIGHEST POPULATION

THE WORLD POPULATION AND THE TOP TEN COUNTRIES WITH THE HIGHEST POPULATION The ten countries with the largest population in the world are China, India, United States, Indonesia, Brazil, Pakistan, Bangladesh, Nigeria, Russia and Japan.

TOP TEN COUNTRIES WITH THE HIGHEST POPULATION # Country 2000 Population 2010 Population 2014 Population 2050 Expected Pop. 1 China 1,268,853,362 1,330,141,295 1,355,692,576 1,303,723,332 2 India 1,004,124,224 1,173,108,018 1,236,344,631 1,656,553,632 3 United States 282,338,631 310,232,863 318,892,103 439,010,253 4 Indonesia 213,829,469 242,968,342 253,609,643 313,020,847 5 Brazil 176,319,621 201,103,330 202,656,788 260,692,493 6 Pakistan 146,404,914 184,404,791 196,174,380 276,428,758 7 Nigeria 123,178,818 152,217,341 177,155,754 264,262,405 8 Bangladesh 130,406,594 156,118,464 166,280,712 233,587,279 9 Russia 146,709,971 139,390,205 142,470,272 109,187,353 10 Japan 126,729,223 126,804,433 127,103,388 93,673,826 TOP TEN Countries 3,618,894,827 4,016,489,082 4,176,380,247 4,950,140,178 Rest of the World 2,466,012,769 2,829,120,878 3,005,478,372 4,306,202,522 TOTAL World Population 6,084,907,596 6,845,609,960 7,181,858,619 9,256,342,700 NOTES: (1) The Top 10 Most Populated Countries of the World Table was updated for August 12, 2014. (2) Detailed data for individual countries may be found clicking on each country name. (3) Demographic (population) estimates for years 2000, 2010, 2014 and 2050 are based mainly on mid-year data from the US Census Bureauwebsite, and verified with local census agencies, when available. (4) The China population data is for the mainland only. (5) Data from the Internet World Stats website may be cited, giving the due credit and establishing an active link back to Internet World Stats. (6) For definitions, navigation help and methodology, see the Site Surfing Guide. Copyright © 2001 - 2014, Miniwatts Marketing Group. All rights reserved worldwide.

Why do businesses grow?

There are many reasons that help to explain the motivations for businesses to grow

1. Profit motive:

• Businesses grow to achieve higher profits and provide better returns for shareholders
• The stock market valuation of a firm is influenced by expectations of future sales and profit streams so if a company achieves disappointing growth figures, this can be reflected in a fall in the share price. This opens up the risk of a hostile take-over and also makes it more expensive for a quoted company to raise fresh capital by issuing new shares

2.Cost motive:

• Economies of scale the long run increase the productive capacity of the business leading to lower average costs. They help to raise profit margins at a given market price

3.Market power motive:

1. Firms may wish to increase market dominance giving them increased pricing power
2. This market power can be used as a barrier to the entry of new businesses in the long run
3. Larger businesses can build and take advantage of buying power (monopsony power)

4.Risk motive:

1. Growth might be motivated by a desire to diversify production and/or sales so that falling sales in one market might be compensated by stronger demand in another sector
2. This is known as achieving economies of scope and is a feature of conglomerates

5.Managerial motives: Behavioural heories of the firm predict that business expansion might be accelerated by senior and middle managers whose objectives differ from major shareholders.

Daily active users on Facebook

The number of installed users of a product is one of the metrics used by businesses to measure how fast they are growing. This is especially important for network businesses such as Facebook. The chart shows the number of active daily users of the social media site.

|