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concepts_ch4

# 3b conceptest two lightbulbs a and b are two

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Unformatted text preview: ed in series to a constant voltage source. When a wire is connected across B, bulb A will: across Short Circuit II a) glow brighter than before glow b) glow just the same as before glow c) glow dimmer than before glow d) go out completely e) explode Since bulb B is bypassed by the wire, the total resistance of the circuit decreases. This means that the current decreases through bulb A increases. through Follow-up: What happens to bulb B? ConcepTest 4.4a ConcepTest The lightbulbs in the circuit below The are identical with the same resistance R. Which circuit Which produces more light? (brightness ⇐⇒ power) ⇐⇒ Circuits I a) circuit 1 circuit b) circuit 2 circuit c) both the same both d) it depends on R ConcepTest 4.4a ConcepTest The lightbulbs in the circuit below The are identical with the same resistance R. Which circuit Which produces more light? (brightness ⇐⇒ power) ⇐⇒ In #1, the bulbs are in parallel, parallel lowering the total resistance of the lowering circuit. Thus, circuit #1 will draw #1 a higher current, which leads to higher more light, because P = I V. Circuits I a) circuit 1 circuit b) circuit 2 circuit c) both the same both d) it depends on R ConcepTest 4.4b ConcepTest Circuits II The three lightbulbs in the circuit all have The a) twice as much twice the same resistance of 1 Ω . same b) the same the By how much is the brightness of bulb B greater or smaller than the brightness of bulb A? brightness (brightness ⇐⇒ power) ⇐⇒ c) 1/2 as much 1/2 d) 1/4 as much e) 4 times as much A C B 10 V ConcepTest 4.4b ConcepTest Circuits II The three light bulbs in the circuit all have The a) twice as much twice the same resistance of 1 Ω . same b) the same the By how much is the brightness of bulb B greater or smaller than the brightness of bulb A? brightness (brightness ⇐⇒ power) ⇐⇒ c) 1/2 as much 1/2 d) 1/4 as much e) 4 times as much A We can use P = V2/R to compare the power: C B PA = (VA)2/RA = (10 V) 2/1 Ω = 100 W 100 PB = (VB)2/RB = (5 V) 2/1 Ω = 25 W 25 Follow-up: What is the total current in the circuit? 10 V ConcepTest 4.5a Conc...
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