Munali Boys High School/CURRENT ELECTRICITY/CHAPTER 2: ELECTRIC CIRCUITS
Contents
CHAPTER 2: ELECTRIC CIRCUITS
This chapter is meant for pupils of physics in high schools.
| Before the chapter, pupils should do the basics of current electricity,namely: current, voltage,potential difference and effective resistance |
| At the end of this topic pupils should be able to define an electric circuit,distinguish between a series and a parallel circuit,calculate effective resistance,current and potential difference in cicuits |
| Pupils should do an exercise at the end of the notes below |
| An electric circuit is a path in which current flows.An example of this may be a single copper wire whose two ends are connected to a battery |
TWO TYPES OF CIRCUIT
There are two types of electric circuits.These are:
- Series Circuit
- Parallel Circuit
| A series circuit is one in which the components come one after the other along the same loop |
| A parallel circuit is one in which the components (resistors) are connected in separate loops |
{{Key points|On Series and Parallel circuits:
- In a series cicuit the formula below is used to calculate the effective resistance.
R = r1 + r2 + r3.... Where: R = effective resistance and r1,r2 and r3.... are the given
resistance values.
If the resistors are connected in parallel their effective resistance is found from the formula below.
1/R = 1/r1 + 1/r2 + 1/r3.........
- The current is the same everywhere in a series circuit. Therefore, same current flows through every component.
In a parallel circuit current is shared by the components(resistors).The higher the resistance of a component, the lower is the current that flows through it.In both cases(series and parallel circuits),current is calculated calculated from the formula: I = V/R Where: I = current, V = voltage and R = effective resistance
- In series and parallel connections, the potential difference is found from the formula below
P.d = Ir where: P.d = potential difference across a component
I = current through the component
r = resistance of a component
In a series circuit the p.d depends on the resistance of a component.The higher the resistance the higher is the p.d across it.In a parallel circuit the p.d across each resistor is the same.Therefore, p.d acros r1=p.d across r2 = p.d across r3 etc.
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