Part A Learning Goal: To understand the concept of electromotive force and internal resistance; to understand For the circuit shown on the left in (Figure 1), which potential difference corresponds to the terminal voltage of the battery? the processes in one-loop circuits; to become familiar with the use of the ammeter and voltmeter. In order for the current in a conductor to exist continuously, the conductor must be part between points K and L of a loop, that is, a closed path through which the charged particles can move without creating a "build-up." Such build-up, if it occurs, creates its own electric field that cancels between points L and M out the external electric field, ultimately causing the current to stop. between points K and M However, having a loop, or a closed circuit, is not enough to maintain the current; there must also be a source of energy. Its necessity is fairly obvious: As charged particles move along the circuit, they lose potential energy. In fact, electrostatic forces always Submit Request Answer push the particles in the direction that leads to a decrease in potential energy. At some point, each charged particle would reach the location in the circuit where it has the lowest possible potential energy. How can such a particle move toward a point where it would have a higher potential energy? The next several questions refer to the four diagrams on the left in (Figure 2) shown here labeled A, B, C, and D. Such a move requires that nonelectrostatic forces act upon the charged particle, pushing it toward higher potential energy despite the presence of electrostatic forces. In circuits, such forces exist inside a device commonly known as a battery. In a circuit, the Part B battery serves as the energy source that keeps the charged particles in continuous motion by increasing their potential energy through the action of some kind of nonelectrostatic force. In which diagram(s) (labeled A - D) is the ammeter connected correctly to measure the current through the battery? The amount of work that the battery does on each coulomb of charge that it "pushes Select the letter(s) corresponding to the correct diagram(s). through" is called (inappropriately) the electromotive force (pronounced "ee-em-ef" and abbreviated emf or denoted by &). Batteries are often referred to as sources of emf View Available Hint(s) (rather than sources of energy, even though they are, fundamentally, sources of energy). The emf of a battery can be calculated using the definition mentioned above: E = W/q. The units of emf are joules per coulomb, that is, volts. A The terminals of a battery are often labeled + and - for "higher potential" and "lower Q B potential," respectively. The potential difference between the terminals is called the terminal voltage of the battery. If no current is running through a battery, the terminal O C voltage is equal to the emf of the battery: A Vbat = &. D However, if there is a current in the circuit, the terminal voltage is less than the emf because the battery has its own internal resistance (usually labeled r). When charge q passes through the battery, the battery does the amount of work &q on the charge; Submit however, the charge also "loses" the amount of energy equal to Ir ( I is the current through the circuit); therefore, the increase in potential energy is &q - qIr, and the terminal voltage is AVbat = E - IT. Part C Complete previous part(s) In order to answer the questions that follow, you should first review the meaning of the Part D Complete previous part(s) symbols describing various elements of the circuit, including the ammeter and the voltmeter; you should also know the way the ammeter and the voltmeter must be connected to the rest of the circuit in order to function properly Part E Complete previous part(s) Note that the internal resistance is usually indicated as a separate resistor drawn next to the "battery" symbol. It is important to keep in mind that this resistor with resistance r is Part F Complete previous part(s) actually inside the battery. Figure Part G Complete previous part(s) 1 of 2 Part H Complete previous part(s) Part I Complete previous part(s) M Part J Complete previous part(s) Part K Complete previous part(s) R Part L Complete previous part(s) Part M Complete previous part(s)