Physics test monday

• What is the purpose of circuit symbols in electric circuit diagrams?


  They are used to create diagrams that can be understood universally.
• What are the symbols for the following components in a circuit: cell, battery, switch, voltmeter, ammeter, fixed resistor, variable resistor, filament lamp, motor, diode, thermistor, LDR, LED?


  • Cell: |
  • Battery: ||
  • Switch: O
  • Voltmeter: V
  • Ammeter: A
  • Fixed Resistor: Rectangle
  • Variable Resistor: Rectangle with an arrow
  • Filament Lamp: Circle with a zigzag line
  • Motor: Circle with "M"
  • Diode: Triangle pointing to a line
  • Thermistor: Circle with a line and a temperature symbol
  • LDR: Circle with a line and a light symbol
  • LED: Circle with a line and a light symbol with arrows
• What are the four components commonly used to change or control the amount of resistance in a circuit?

  Thermistor, LDR, fixed resistor, variable resistor.
• How does a thermistor behave with temperature changes?


  Resistance decreases when the temperature increases.
• How does an LDR behave with light intensity changes?


  Resistance decreases when the light intensity increases.
• What is the main difference between an LED and a filament lamp?


  An LED will only allow electrical current to pass through it in one direction.
• What are the differences in current and potential difference in series and parallel circuits?


  Series Circuits:

  • Current is the same at every point.
  • Potential difference adds up across components.

  
  

  Parallel Circuits:

  • Current splits and recombines at junctions.
  • Potential difference is the same across each branch.
• Why are ammeters connected in series with components?


  To measure the current flowing through the component accurately.
• What happens to the size of the current in a series circuit?


  The current is the same value at any point in the series circuit.
• What is the formula to calculate charge?


  Charge (C) = current (A) x time (s).
• If a current of 1.5 A flows for 2 minutes, how much charge flows?


  $Q =$$1.5 \text{ A} \times 120 \text{ s} =$$180 \text{ C}$
• If a charge of 1200 C flows through a filament lamp for 4 minutes, what is the average current?


  $I =$$\frac{1200 \text{ C}}{240 \text{ s}} =$$5 \text{ A}$
• How do you calculate the charge that flows in one hour with a current of 0.25 A?


  $Q =$$0.25 \text{ A} \times 3600 \text{ s} =$$900 \text{ C}$
• What is the relationship between energy, charge, and potential difference in electrical circuits?


  • Energy transferred (J) = Charge (C) x Potential difference (V)
• What is the relationship between current and charge in a series circuit?


  The current is the same value at any point in a series circuit.
• What are the units of current and charge?


  The units of current are Amperes (A) and the units of charge are Coulombs (C).
• How do you calculate the charge that flows when a current of 1.5 A flows for 2 minutes?


  Q = I × t = 1.5 A × 120 s = 180 C.
• If a charge of 1200 C flows through a filament lamp for 4 minutes, what is the average current?


  The average current is 5 A.
• How do you calculate the charge that flows in one hour with a current of 0.25 A?


  Q = I × t = 0.25 A × 3600 s = 900 C.
• What is the relationship between energy, charge, and potential difference?


  Energy is related to charge and potential difference by the equation E = Q × V.
• How do you calculate energy transferred when a charge of 25 C passes through a motor with a potential difference of 6 V?


  E = Q × V = 25 C × 6 V = 150 J.
• If a current of 1.2 A flows through a bulb for 2 minutes at a potential difference of 12 V, how much energy is transferred?


  E = I × t × V = 1.2 A × 120 s × 12 V = 1728 J.
• How do you calculate the potential difference across a resistor if a charge of 18 C transfers 364 J of electrical energy?


  V = E / Q = 364 J / 18 C = 20.2 V.
• Why is the volt defined as a "joule per coulomb"?


  Because it represents the energy transferred per unit charge.
• How do you calculate the current passing through a resistor if the potential difference is 18 V and it transfers 500 J in 4 minutes?


  First, calculate the energy transferred per second, then use I = V / R.
• What does Ohm's law state about the relationship between current, potential difference, and resistance?


  Ohm's law states that the current is directly proportional to the potential difference at constant temperature.
• What is the equation for Ohm's law?


  V = I × R.
• What are the units for resistance?


  The units for resistance are Ohms (Ω).
• How do you calculate the resistance of a resistor if the current flowing through it is 3 A and the potential difference across it is 15 V?


  R = V / I = 15 V / 3 A = 5 Ω.
• What are the characteristics of resistors in series?


  • The current through each resistor is the same.
  • The sum of the voltages across the resistors equals the cell voltage.
• What are the characteristics of resistors in parallel?


  • The total current leaving the battery equals the sum of the currents in the branches.
  • The potential difference across each resistor is equal to the battery's potential difference.
• How do you calculate the total current supplied by the battery in a parallel circuit with two resistors?


  Total current = current through resistor X + current through resistor Y.
• If two resistors, each of resistance 60 ohms, are arranged in series and connected to a 12 V cell, how do you calculate the current flowing in the circuit?


  Use I = V / R, where R = 60 Ω + 60 Ω = 120 Ω.
• How does the arrangement of resistors affect the total resistance in a circuit?


  In series, total resistance increases; in parallel, total resistance decreases.
• What is the significance of a variable resistor in a circuit?


  A variable resistor allows for changing the resistance and thus controlling the current flow.
• How do you plot a current against potential difference graph for a resistor?


  Vary the potential difference and measure the current, then plot the values on a graph.
• What does a steeper line on a current versus potential difference graph indicate about a resistor?


  A steeper line indicates a lower resistance in the resistor.
• What is the formula for calculating the current through a resistor?

  I = V / R.
• If a current of 3.2 A flows through a lamp with a resistance of 18 Ω, how do you calculate the potential difference across the lamp?


  Use V = I × R = 3.2 A × 18 Ω.
• How do you calculate the resistance of a resistor if the current flowing through it is 0.4 A and the potential difference is 28 V?


  R = V / I = 28 V / 0.4 A.