Series and Parallel circuits

• In series circuits, the total resistance is equal to the sum of all resistors.
• Resistance is the ratio of current flowing through conductors to the voltage across it
• R=v/i = 1/t = 1/t0
• longer/thicker the wire the more resistance
• • Current: amperes/amps (A)
  • Charge: coulombs (C)
  • Energy: joules (J)
  • Resistance: ohms (Ω)
  • Time: seconds (s)
  • Voltage: volts (V)
  • Power: watts (W)
• Earthing: connects the metal body of an appliance to the Earth's conducting surface, creating a safe pathway for electric current in case of a fault, preventing electric shock.
• When a current flows through a resistor, it transfers electrical energy into heat due to a process called Joule heating
• power=current x voltage
• energy transfered = current x voltage x time
• Current (I) is the rate at which electric charge flows through a conductor, measured in amperes (A)
• Voltage (V) represents the electrical potential difference or the force that drives the current, measured in volts (V).
• Direct current flows in one direction, typically provided by cells or batteries.
• Alternating current periodically changes direction, commonly supplied by the mains electricity grid.
• DC is used in small electronic devices, while AC is used for powering homes and most electrical appliances.
• Advantages of parallel circuits:

  • Components (e.g. bulbs) may be switched on/off independently.
  • If one component breaks, current can still flow through the other parts of the circuit.
  • Bulbs maintain a similar brightness.
• Advantages of series circuits:

  • Fewer wires, cheaper and easier to assemble.
  • Uses less power
• • As voltage increases the current also increases.
• • In general, the more components in a circuit, the lower the current.              
• A filament Lamp, Ohmic Resistor, Diode

  A) ?

  B) ?

  C) ?

  
• Wires: In ideal wires, current is directly proportional to voltage (Ohm's Law). Real wires have a small resistance, causing a slight voltage drop.
• Resistors: Current through a resistor is directly proportional to the voltage across it (Ohm's Law).
• • Metal filament lamps: Current and voltage have a nonlinear relationship, often exponential, due to the positive temperature coefficient of the filament material.
• • Diodes: Diodes have a highly non-linear current-voltage relationship. They conduct current when forward-biassed and act as insulators when reverse-biassed.
• LDR are devices whose resistance varies with the amount of incident light.
• As illumination increases, resistance decreases.
• • The resistance change in LDRs is typically non-linear. The resistance decreases rapidly at first with increasing illumination and then levels off at higher light intensities.
• Thermistors, on the other hand, are temperature-sensitive resistors. Their resistance varies with changes in temperature. 
• As temperature increases, resistance decreases.
• Lamps and LEDs can be used as indicators to detect the presence of a current in a circuit.
• Potential difference (V) = Current (A) x Resistance (Ω) 
• Charge flows from the positive terminal to the negative terminal

  
• Q (charge) = I (current) × t (time)
• Some of the electrons become free from the orbit. Therefore in solid conductors, the current is carried by the negatively charged electrons.

  
• At a junction current ‘splits’ to take both paths.

  It comes back together when the paths meet again.

  A) Junction

  
• Electrons are physical matter – they cannot be created or destroyed. This means the total number of electrons (and hence current) going around a circuit must remain the same.
• I1 = I2 + I3 +I4

  
• The voltage across components connected in parallel is the same as the supply voltage for each component. VT = V1 = V2

  
• V = IR where V = voltage, I=current, R=resistance
• VT = V1 + V2

  IT = I1 = I2

  RT = R1 + R2

  
• Energy transferred (J) = charge (C) x voltage (V)