Figure 19.73 is a top view of a portion of a circuit containing three identical light bulbs (the rest of the circuit including the batteries is not shown). The connecting wires are made of copper. (a)...

Figure 19.73 is a top view of a portion of a circuit containing three identical light bulbs (the rest of the circuit including the batteries is not shown). The connecting wires are made of copper.

(a) The compass is placed on top of the wire, and it deflects 20 degrees away from north as shown (the wire is

underneath the compass). In what direction are the electrons moving at location P1? How do you know?

(b) In the steady state, 3 × 1018 electrons pass location P1 every second. How many electrons pass location P2 every

second? Explain briefly.

(c) Give the relative brightnesses of bulbs B1, B2, and B3. Explain briefly.

(d) There are 6.3 × 1028 mobile electrons per cubic meter in tungsten. The cross-sectional area of the tungsten filament

in bulb B1 is 0.01 mm (which is 1 × 10−8 m2. The electron mobility in hot tungsten is 1.2 × 10−4 (m/s)/(N/C).

Calculate the electric field inside the tungsten filament in bulb B1. Give both the direction and the magnitude of the

electric field.