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NCEA L2 D.C. Electricity

NCEA L2 D.C. Electricity. What is electrical current?. ANS: Electric current is the flow (movement) of electric charge. Symbol : I Units: Amperes (A). DO EXERCISES PAGE 156 RUTTER. I = q/t. Where I = current in amps (A) q = charge in Coulombs (C) t = time (s).

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NCEA L2 D.C. Electricity

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  1. NCEA L2 D.C. Electricity

  2. What is electrical current? ANS: Electric current is the flow (movement) of electric charge. Symbol : I Units: Amperes (A) DO EXERCISES PAGE 156 RUTTER I = q/t Where I = current in amps (A) q = charge in Coulombs (C) t = time (s) Current is measured with an ammeter placed in series in the circuit Conventional current is where electrons travel from +ve to –ve. Natural current is where it travels from a build up of –ve charge to an area deficient in –ve charge namely and area of +ve charge

  3. What is electrical energy ANS: Voltage (sometimes also called electric or electrical tension) is the difference of electric potential between two points of an electrical or electronic circuit, expressed in volts Symbol : V Units: Volts (V) V = I/q Where V = voltage in volts (V) I = current in amps (A) q = charge in Coulombs (C) Often thought of as the change in energy as the charge moves between two points.

  4. Thus: E = Vq Where E = change in energy (J) V = voltage in volts (V) q = charge in Coulombs (C) DO EXERCISES PAGE 157 -8 RUTTER F = Eq Where E = electric field strength F = force on the charge (N) q = charge in Coulombs (C) The voltage between two points, distance apart ‘d’, in an electric field ‘E’ V = Ed

  5. What is electrical power? ANS: is defined as the rate at which electrical energy is transferred by an electric circuit. Symbol : P Units: Watts (W) P = IV DO EXERCISES PAGE 158 - 9 RUTTER Where P = power in watts (W) I = current in amps (A) V = voltage in volts (V)

  6. WHAT IS RESISTANCE? ANS: is defined as a measure of the degree to which an object opposes an electric current through it Symbol : R Units: Ohms (Ω) V = IR Where R = resistance in ohms (Ω) I = current in amps (A) V = voltage in volts (V) Resistance occurs in all conductors. A good conductor has low resistance and vice versa. The current in a conductor depends on the resistance and the voltage applied across it, Ohm’s Law). Resistance often very large kΩ or MΩ

  7. RESISTANCE IN SERIES & PARALLEL V V I I1 I A1 A A I2 I A2 R2 R1 R2 A3 V1 V2 R3 I3 SERIES PARALLEL • The current, I, measured by each ammeter has the same value in each part of the circuit. • The voltages across the series resistors add up to the supply voltage Vs = V1 + V2. • The equivalent resistance, Rs, of the whole circuit is given by: Rs = R1 + R2. • The currents in the parallel components add up to the current from the supply, ie I1 = I2 + I3. • The voltage is the same across all branches in parallel • The equivalent resistance, Rs, of the whole circuit is given by: 1/Rp = 1/R2 + 1/R3.

  8. READ INFORMATION PAGE 162 - 163 COMPLETE RELEVANT EXERCISES FROM RUTTER

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