Resistance & Ohm's Law

• Resistance: opposition to current.
• Resistance occurs because free electrons flowing in the circuit collide with metal ions in the wire.

  These collisions slow down electron flow.
• The higher the resistance, the lower the current.
• Total resistance in Series circuits:

  • Total resistance = sum of individual resistances, because the current must pass through each resistor in sequence.
  • As you increase the number of resistors, the total resistance of the circuit increases.
  • $R_T=$$R_{1\ }+$$\ R_2+$$\ R_3$
• Resistance in Parallel circuits:

  • In parallel circuits, current can split and travel through several branches simultaneously.
  • As you increase the number of resistors and pathways, the total resistance of the circuit decreases.
  • $\frac{1}{R_T}=$$\frac{1}{R_1}+$$\frac{1}{R_2}+$$\frac{1}{R_3}\$
• When you calculate total resistance, the unit symbol is?

  $\Omega$
• trend of resistance in series circuit:

  when the number of resistors or loads increases, the resistance decreases in the circuit increases.
• trend of resistance in parallel circuits:

  when the number of resistors or pathways increases, the resistance of the circuit decreases.
• calculating total resistance of series circuits:

  RT= R1 + R2 + R3 + ...
• calculating total resistance of parallel circuits:

  1/RT = 1/R1 + 1/R2 + 1/R3 + ...
• Resistance is the opposition to current and is measured in ohms.

  • the resistance controls the size of the current in a circuit.
• Ohms Law states that the voltage across a conductor is directly proportional to the current flowing through it.

  • V = I x R
  • I = V/R
  • R = V/I