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Published byClemence Caldwell Modified over 4 years ago

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ELECTRIC CURRENT Electricity, like water, can only flow if charged particles have potential.

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An electron in motion defines an electric current. e-e- In fact, any charged particle that moves defines an electric current.

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Na + A moving sodium ion, for example, defines an electric current

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The rate of flow of electric charges is how we measure current e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- One coulomb of electric charges per second passing through a conductor is 1 ampere, or 1 “amp”.

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1 Coulomb 1.6 x 10 -19 C/e - = 6.28 x 10 18 electrons Remember… So: 1 Coulomb/second = 6.28 x 10 18 e - /s 1 amp = 6.28 x 10 18 fundamental charges/sec Current is abbreviated as: I

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What is the relationship between potential and flow? There is a direct relation between potential and flow

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So: IV But, some conductors allow for greater flow than others.

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So, the RESISTANCE (R) to flow must also be considered. We can say that resistance is INVERSELY PROPORTIONAL to flow. So: I

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THEREFORE: When we put everything together, This equation is known as Ohm’s Law

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In the world of electricity, the electrical potential is the VOLTAGE (V) It represents the energy per unit charge. Remember that 1 Volt = 1 Joule/Coulomb

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Unit summary: Electrical potential = current = = volt = amp

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So, if then R =R = This unit is far more commonly known as the OHM = Ω

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RESISTANCE Depends on three factors: 1.The type of material (ρ) 2. The length of the conductor (L) 3. The cross-sectional area of the conductor (A)

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RESISTIVITY (ρ) It varies with temperature In general, the resistivity INCREASES with increasing temperature

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CIRCUITS In order for electricity to be useful, it must flow in a closed circuit. The source of potential (voltage) must have a closed pathway for current to flow. With few exceptions, all circuits have some resistance to current flow.

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These symbols are found in your reference tables and provide the standard symbols for circuit components.

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These diagrams represent circuits found on Regents Exams. Can you identify the symbols?

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TYPES OF CIRCUITS There are two basic types: Series Parallel

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A series circuit has all of the resistors in line with the conductor

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Parallel Circuits Resistors are arranged in parallel along more than one conductor.

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Series or parallel?

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Note that the ammeter is placed in series

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Note that the voltmeter is placed in parallel.

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