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# Electric circuits - grade 12

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Grade 12 summary presentation for physics: electric circuits

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### Electric circuits - grade 12

1. 1. 1 Everything Science www.everythingscience.co.za 10. Electric circuits Physics Grade 12
2. 2. 2 Everything Science www.everythingscience.co.za Revision Ohm’s Law governs the relationship between current and potential difference for a circuit element at constant temperature. Mathematically we write: Conductors that obey Ohm’s Law are called ohmic conductors; those that do not are called non- ohmic conductors. Ohm’s Law can be applied to a single circuit element or the circuit as a whole (if the components are ohmic). I= V R
3. 3. 3 Everything Science www.everythingscience.co.za Series and parallel circuits The equivalent resistance of resistors in series (Rs ) can be calculated as follows: The potential difference and current for series circuits is given by: The equivalent resistance of resistors in parallel (Rp ) can be calculated as follows: The potential difference and current for parallel circuits is given by: Rs=R1+R2+R3+ … +Rn VT=V 1+V2+V 3+ … +V n IT=I1=I2=I3= … =In 1 Rp = 1 R1 + 1 R2 + 1 R3 + … + 1 Rn IT=I1+I2+I3+ … +In VT=V 1=V2=V3= … =V n
4. 4. 4 Everything Science www.everythingscience.co.za Internal resistance Real batteries have an internal resistance. The potential difference V of the battery is related to its emf Ɛ and internal resistance r by: The external resistance (R) in the circuit is referred to as the load. ℇ=V +Ir
5. 5. 5 Everything Science www.everythingscience.co.za For more practice see: everythingscience.co.za Shortcode: ESCQ2
6. 6. 5 Everything Science www.everythingscience.co.za For more practice see: everythingscience.co.za Shortcode: ESCQ2