Which statement does not explain the concept of the doppler effect? a) as an observer approaches a stationary sound, the sound waves are compressed, making the pitch higher. b) as an observer moves away from a stationary sound, the sound waves are stretched making the pitch lower. c) as a sound source approaches a stationary object, the sound waves are compressed, making the pitch higher. d) as a sound source moves away from a stationary object, the sound waves are compressed, increasing the pitch.

(2) (a) you have a simple circuit that consists of only a battery (δvbat=1.5v) and two resistors with resistance r1=10ω and r2=5ω, connected in series with each other. what is the current running through the battery? (b) you re-arrange your circuit so now r2 is attached in parallel to r1 rather than in series. what is the current running through the battery? (c) you add an additional resistor r3=7ω on the same branch as r2. what is the current running through the battery? (d) what is the power dissipated in r3?