# Quiz 18: Direct-Current Circuits

Physics & Astronomy

No, it depends on the emf of the battery. If the battery has a more emf, than the source emf then the battery acts as a source to the circuit. In such situation, the current will flows from the negative terminal to the positive terminal of the battery. If the battery has less emf than the source emf, then the current will flows from the positive terminal of the battery to the negative terminal of the battery.

The relation between the current I and the emf of the battery in presence of internal resistance r of the battery is shown below. Here, R is the load resistance and r is the internal resistance. Re-arrange the equation to solve for r. Substitute 9.00 V for , 0.117 mA for I , and . Therefore, the internal resistance r of the battery is .

Three light bulbs are in series connection with a battery supply of V is as shown in figure 1. Figure 1 Three Light bulbs are in parallel connection with a battery supply of V is as shown in figure 2. Figure 2 Two Light bulbs are in series connection and the resultant brightness of these two in parallel with third light bulb with a battery supply V is as shown in figure 3. Figure 3 Two Light bulbs are in parallel connection and the resultant brightness of these two in series with third light bulb with a battery supply V is as shown in figure 4. Figure 4 Therefore, the possible connections obtained for three bulbs and a battery are 4.