O level Dynamics
Use the following learning outcomes to design a lesson to learn O level science physics
Learning Outcomes
(a) state that there are positive and negative charges and that charge is measured in coulombs
(b) state that unlike charges attract and like charges repel
(c) state that current is the rate of flow of charge and that it is measured in amperes
(d) distinguish between conventional current and electron flow
(e) recall and apply the relationship charge = current × time to new situations or to solve related problems
(f) state that the electromotive force (e.m.f.) of an electrical source of energy is measured in volts
(g) state that the potential difference (p.d.) across a component in a circuit is the work done per unit charge in driving charges through the component and that it is measured in volts
(h) state that resistance = p.d. / current
(i) apply the relationship R = V / I to new situations or to solve related problems
(j) recall and apply the relationship of the proportionality between resistance and the length and cross-sectional area of a wire to new situations or to solve related problems
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Electric charge is a fundamental property of matter. There are two types of electric charges: positive and negative. Charge is measured in coulombs. Unlike charges attract each other, while like charges repel. The elementary charge of an electron is 1.6 times 10 to the power of minus 19 coulombs.
Electric current is the rate of flow of electric charge, measured in amperes. Current equals charge divided by time. There are two ways to describe current direction: conventional current flows from positive to negative terminal, while electron flow is actually from negative to positive. The relationship between charge, current and time is given by Q equals I times t.
Electromotive force or EMF is the energy provided by an electrical source like a battery, measured in volts. Potential difference is the work done per unit charge when driving charges through a circuit component, also measured in volts. We can understand voltage using a water analogy: just as water pressure drives water flow through pipes, voltage drives electric current through circuits.
Resistance is the opposition to electric current flow, measured in ohms. Ohm's Law states that resistance equals voltage divided by current, written as R equals V over I. This fundamental relationship shows that voltage and current are directly proportional for ohmic materials. For example, if voltage is 12 volts and current is 3 amperes, then resistance equals 4 ohms.
Wire resistance depends on two main physical factors. First, resistance is proportional to length - longer wires have more resistance because electrons encounter more collisions. Second, resistance is inversely proportional to cross-sectional area - thicker wires have less resistance because there's more space for current flow. The complete relationship is R equals rho L over A, where rho is the material's resistivity.