P2 3.Electrical circuits

P2 3.Electrical circuits

1. 3.1 Static electricity

   • When you rub a balloon it becomes electrically charged and attracts other materials.
     • You charge any other insulating materials in a similar way.
     • An object get charged when it gets covered in negitively charged electrons.
     • The potential difference (p.d.), or voltage, between two points in a circuit is work done, or energy transfered, per coulomb of charge passing through the circuit.
       • V = W/Q
         • V is the p.p in volts (V), W is the work done in joules (J) and Q is the electrical charge in colombs (C).

2. 3.2 Current, potential difference and resistance

   • Ohm's law: V = IR
     • V = potential difference in volts (v), I = current in amps (A) and R = resistance in ohms (Special Omhs sign)
   • LDRs is a light dependant resistor. It is a resistor to control the flow of current in a elecrical circuit

3. 3.3 Non-ohmic conductors

   • Some components don't follow Ohm's law. For example a filament bulb is a ordinary bulb. The tungsten filament in the bulb conducts electricity well. But its resistance changes the hotter it gets. the more current, the hotter it gets. Meaning its harder to push the current through the circuit.
   • LEDs are a even more efficient than other bulbs as they last for hundreds of times longer than filament bulbs . But they are very expensive

4. ·

   • In a series circuit, the total p.d. from the power supply is shared between the components.
     • Potential difference across each resistor = total p.d. x resistance of resistor/ total resistance

5. 3.5 Parallel Circuits

   • it contains at least one place where the circuit splits into two or more seperate currents.
   • the p.d. is the same across each component of a parallel circuit.
   • The resistance of each branch determmines how the current splits.
     • the larger the resistance of the branch, the smaller the current flows down.

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