A student constructs an electrical circuit using a battery, three single-pole switches (K1K_1K1, K2K_2K2, and K3K_3K3), and two identical filament indicator lamps (D1 D_1\,D1 and D2D_2D2), connected as shown in the diagram below:
Which switch or switches must the student close so that only lamp D1 D_1\,D1 lights up?
Which switch or switches must the student close so that only lamp D2 D_2\,D2 lights up?
All three switches are now closed so that both lamp D1 D_1\,D1 and lamp D2 D_2\,D2 light up.
Which sentence correctly describes the brightness of the two lamps?
- Both lamps have the same brightness.
- Lamp D1 D_1\,D1 is brighter than lamp D2D_2D2.
- Lamp D2 D_2\,D2 is brighter than lamp D1D_1D1.
Explain your answer to (c).
Complete the following sentences to explain what happens to the metal lattice inside a filament lamp when the current increases. Use words from the list below:
- anions
- atoms
- decreases
- electrons
- increases
- ions
- thermal
- vibrate
As the electric current increases, the moving free .................... collide more frequently with the positive .................... in the metal lattice. This lattice disturbance .................... the overall electrical resistance of the wire.