IB Physics SLGOHS

Chapter 17-19 Test Review ANSWERS

  1. In a certain material there is a current of 16 A flowing through a surface to the right, and there is an equal amount of positive and negative charge passing through the surface producing the current. How much negative charge passes through the surface?(8 C/s to the left)
  2. Materials having resistance changes as voltage or current varies are called:(non-ohmic)
  3. You measure a 25.0-V potential difference across a 5.00-Ω resistor. What is the current flowing through it?(5 A)
  4. A metallic conductor has a resistivity of 18 x 10-6Ωm. What is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 x 10-6 m2?(180 Ω)
  5. When a positive charge moves in the direction of the electric field, what happens to the electrical potential energy associated with the charge?(decreases)
  6. A wire carries a steady current of 0.1 A over a period of 20 s. What total charge moves through the wire in this time interval?(2 C)
  7. What is the potential difference across a 5.0 Ω resistor that carries a current of 5.0 A?(25 V)
  8. What affects a material’s resistance?(length, area, type of material, temperature of material)
  9. If a 75 W light bulb operates at a voltage of 120 V, what is the current in the bulb?(0.62 A)
  10. If a 325 W heater has a current of 6.0 A, what is the resistance of the heating element?(9 Ω)
  1. What happens when the switch is closed in the circuit shown above?(Light goes out bc it short circuits)
  2. Is the terminal voltage of a battery equal to its emf? Explain.(No due to internal resistance)
  3. Three resistors, with values of 2.0, 4.0 and 8.0 Ω, respectively, are connected in series. What is the overall resistance of this combination?(14 Ω)
  1. Which resistor, below, is in series with resistor R?(R4)
  1. When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the current in the bulb as it is warming up?(The current will decrease)
  2. Three 8.0- Ω resistors are connected in parallel. What is their equivalent resistance?(2.7 Ω)
  3. Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 Ω, respectively. If this combination is connected in series with a 12-V battery and a 2.0- Ω resistor, what is the current in the 10- Ω resistor? (Use diagram below) (0.59 A)
  1. Which two resistors, below, are in parallel with each other?(R2 and R3 are in parallel)
  1. Resistors of values 6.0 Ω, 4.0 Ω, 10.0 Ω and 7.0 Ω are combined as shown below. What is the equivalent resistance for this combination?(10.7 Ω)
  1. How much current is flowing in one of the 10- Ω resistors below?(0.8 A)
  1. Which compass needle orientation in the figure above might correctly describe the magnet’s field at that point? (a b/c is in the direction of the magnetic field going from N to S)
  2. A solenoid is in an upright position on a table. A counterclockwise current of electrons—when viewed from above—causes the solenoid to have a ____ magnetic pole at its bottom end. If a compass is placed at the top of the solenoid, the north pole of the compass would be ____. (north magnetic pole causing repulsion of the compass needle)
  3. What can be said about the lines of the magnetic field around a current-carrying wire? (they form concentric circles around the wire)
  4. What are hard magnetic materials? What is a soft magnetic material?(cobalt, nickel, neodymium; iron)
  5. Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following?(convection currents in the liquid core of the earth)
  6. The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following?(south)
  7. A proton moving at a speed of 3.8 x 106 m/s cuts across the lines of a magnetic field at an angle of 70o. The strength of the field is 0.25 x 10-4 T. What is the magnitude of the force acting on the proton? (qp = 1.6 x 10-19 C) (1.4 x 10-17 N)
  8. Below, a stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is:(there is no force on the charge b/c it is not moving and therefore has no magnetic field)
  1. A current-carrying wire of length 50 cm is positioned perpendicular to a uniform magnetic field. If the current is 10.0 A and it is determined that there is a resultant force of 3.0 N on the wire due to the interaction of the current and field, what is the magnetic field strength?(0.60 T)
  2. A wire, below, is lying horizontally in the north-south direction and the horizontal magnetic field is toward the east. Some positive charges in the wire move north and an equal number of negative charges move south. The direction of the force on the wire will be: (down, like going into the page)