4.2.2 Resistance

• Resistance is the opposition to the flow of electric current
• Match the variable with its symbol and units:

  Voltage ↔️ V, Volts

  Current ↔️ I, Amperes

  Resistance ↔️ R, Ohms
• How does increasing the cross-sectional area of a conductor affect its resistance?

  Decreases resistance
• What is the equation for the temperature coefficient of resistance?

  $\frac{\Delta R}{R_{0}} =$$\alpha \Delta T$
• The temperature coefficient of resistance describes how the resistance of a material changes with temperature
• Order the following materials based on their temperature coefficient of resistance from most positive to most negative:

  1️⃣ Copper

  2️⃣ Rubber
• Match the power dissipation equations with their formulas:

  Power = Voltage x Current ↔️ $P =$$IV$

  Power = Current^2 x Resistance ↔️ $P =$$I^{2}R$

  Power = Voltage^2 / Resistance ↔️ $P =$$\frac{V^{2}}{R}$
• Ohm's Law states that voltage is directly proportional to current if temperature remains constant.

  True
• What unit is used to measure resistance?

  Ohms
• What does Ohm's Law state about the relationship between voltage, current, and resistance?

  V = IR
• Match the material with its resistivity characteristic:

  Copper ↔️ Low resistivity

  Rubber ↔️ High resistivity
• In series circuits, the total resistance is the sum of the individual resistances.

  True
• Longer conductors have greater resistance.


  True
• Resistance decreases with a larger cross-sectional area.


  True
• What does the symbol $\alpha$ represent in the temperature coefficient formula?


  Temperature coefficient
• What is the unit of power dissipation in resistors?

  Watts
• In a parallel circuit, the reciprocal of the total resistance is equal to the sum of the reciprocals of the individual resistances
• What is resistance measured in?

  Ohms
• What is the equation for Ohm's Law?

  $V =$$IR$
• How does increasing the length of a conductor affect its resistance?

  Increases resistance
• The temperature coefficient of resistance describes how the resistance of a material changes with temperature
• The resistivity of a material affects its resistance.


  True
• Match the variables in the temperature coefficient of resistance formula with their descriptions:

  \Delta R</latex> ↔️ Change in resistance

  $R_{0}$ ↔️ Initial resistance

  $\alpha$ ↔️ Temperature coefficient

  $\Delta T$ ↔️ Change in temperature
• Power dissipation in a resistor is calculated as the rate at which electrical energy is converted to thermal energy
• In a parallel circuit, the current splits among resistors.


  True
• Order the factors influencing resistance from most to least significant:

  1️⃣ Length

  2️⃣ Cross-sectional area
• Resistance is the opposition to the flow of electric current
• Resistance decreases with larger cross-sectional area
• What is the power dissipated in a resistor if the voltage is 10V and the current is 2A?

  20W
• What is the voltage across a conductor if the current is 3A and the resistance is 5 ohms?

  15V
• How does the length of a conductor affect its resistance?

  Increases with length
• The temperature coefficient of resistance is expressed as \frac{\Delta R}{R_{0}} = \alpha \Delta T
• What happens to the resistance of a good conductor as temperature increases?

  Increases
• How is the total resistance calculated in a series circuit?

  Sum of individual resistances
• Ohm's Law states that voltage is directly proportional to current if temperature remains constant.


  True
• The resistance of a conductor depends on its length, cross-sectional area, and material
• Which material has higher resistivity: copper or rubber?

  Rubber
• A wider path for electrons reduces resistance
• The formula for the temperature coefficient of resistance is $\frac{\Delta R}{R_{0}} =$$\alpha \Delta T$.


  True
• Good conductors have a positive temperature coefficient of resistance.


  True