f5 electricity2

7/30/2019 F5 electricity2

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FORM 5Physics: Electricity

ANALYSING ELECTRIC FIELDS AND CHARGE FLOW

1.Where does charge

come from?

2. Unit of electric

charge?

3. Electric current?

Activity 1

Aim

Apparatus

Procedure 1.Start the motor of a _______________________ generator for a few minutes to produce

positive charges on the metal dome of the generator.2.Bring your finger close to the dome of the generator. Observe what happens

3.Touch the dome of the generator with the free end of the wire that is connected to the

microammeter. Observe the microammeter needle closely.

Observation 1._________________________________________________________________________

2._________________________________________________________________________

3._________________________________________________________________________

4._________________________________________________________________________

Conclusion

Describe an electric

field.


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4.To map the electric

field around metal

electrodes.

Draw the patterns of the electric field.

Describe the effect of

an electric field on a

charge Method.

A charged ball in an electric field.


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Describe the effect of

an electric field on a

charge Method.

The effect of an Electric field on a Candle Flame.


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RELATIONSHIP BETWEEN ELECTRIC CURRENT AND POTENTIAL DIFFERENCE

Describe Potential

Difference?

Definition of Potential

difference.

Potential difference

equation.

What is1 Volt?

How to measure

potential difference?

How to measure

current?

Solve problems

involving

W = QV

1. In a closed circuit, a 6 V battery is used to drive 40 C of electric charge through a

light bulb. How much work is done to drive the electric charge through the bulb?

2. If 72 J of work has to be done to carry 6 C of charge across two parallel metal

plates, what is the potential difference across the metal plates?

Describe the

relationship between

current and potential

difference.

State Ohms Law

Sketch a Graph ofV

against I

What isohmic

conductor and non-

ohmic conductor?


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Define Resistance? The resistance (R) of a conductor is defined as the ratio of the ________________________

across the conductor to the ___________________ flowing through the conductor.

Resistance formula

Good & poor

resistance?

A good conductor has a ____________ resistance and a poor conductor has a ___________

resistance.

Advantage of resistance In a light bulb, the current flowing through a resistance filament causes it to become ______

and then _____________.

Disadvantage of

resistance

Resistance causes some of the electrical energy to turn into__________________ , so some

electrical energy is _______________ along.

Ohms Law equation?

Aim of experiment? To determine the relationship between the potential difference and the electric current

flowing through an______________ and____________________________ conductor.

Hypothesis: The Iflowing through an ohmic conductor is directly proportional to V. It is not

proportional when flowing through an non-ohmic conductor.

Apparatus:

1.

2.3.

4.

5.

6.

7.

Tabulation by drawing

Graph V-I

Ohmic Conductor Non- Ohmic Conductor

Obey Ohms Law Not obey Ohms Law

Factors that affect

resistance?

1.

2.

3.

4.

a)Length factor For conductors of the same material and

cross-sectional area, the resistance R is

_________________ proportional to its length, l

:.where, Rlb)Cross-sectional factor For conductors of the same material and length,

the resistance R is __________________ proportional to its

cross-sectional area, A.

:. Where R lA

c)Type of material

factor

The resistance of a wire depends on

the _________________________

it is made from.

d)Temperature factor For conductors of the same material, length and cross-sectional area, the resistance R

generally __________________________ with temperature.


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Solve problems

involving potential

difference

A current of 0.5 A flows through a length of resistance wire when a potential difference of

12 V is applied between the ends of the wire.

(a) what is the resistance of the wire?

(b) What is the I flowing through the wire if the Vis increased to 15 V?

Resistance ofmetal

and semiconductor?

-The resistance of a____________

increases with temperature

-The resistance of a____________

decreases with temperature.

What is s.w.g number

of wire?

Super-conductor? A superconductor is a material whose

Resistance becomes_____________ when its

temperature ____________ to a certain value

called the ______________________

Advantage of

superconductor?

To maintain a current with no applied voltage at that temperature.

Able to sustain large currents

Smaller power loss during transmission

Less heat energy is wasted

Small-sized motors and generators can be used.

Example of material Element Critical temperature (K)

1. Zinc (Zn)

2. Aluminium (Al)

3. Tin (Sn)

4. Mercury (Hg)

5. Lead (Pb)

6. Niobium (Nb)

Example of

equipment that using

superconductor.

a)MAGLEV trains(Magnetic-levitation). Train can float on superconducting magnets.

b)MRI scanner (Magnetic resonance imaging) is used as diagnostic tool in medicine.

c)Electrical power line (superconductor cable) will increase the efficiency of electrical power

d)To produce computer chips which is small and faster

SERIES AND PARALLEL CIRCUITS

Identify series circuits In a series circuit, two or more resistors are connected one end after another toform a _______________________ path for current flow.

The bulbs share the __________________ from the battery, so each glows dimly.

The brightness of each bulb is _______________ the same since the same current

flows through each bulb.

If one bulb is removed, the other ______________ because the circuit is broken.

Identify parallel circuits All the components are connected with their corresponding ends joined together

to form _____________________________ paths for current flow.

Each bulb gets the full _______________________ from the battery because each

is connected directly to it. So each bulb glows brightly.

The brightness of each bulb in a parallel circuit is ______________ than those in a

series circuit with the same number of bulbs.

If one bulb is removed, the other keeps ________________ because it is still part

of an unbroken circuit.


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Determine the effective resistance of resistors connected in series and parallel.

Series Circuit Parallel Circuit

Diagram

Using Ammeter

Using Voltmeter

Using Ammeter

Using Voltmeter

Current

Potential Difference

Resistance

Brightness of light bulb

Solve the problems


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