EXPERIMENT 5 Equivalence of Energy: Heat, Electrical, Light 0. Pre-Laboratory Wo

Question

EXPERIMENT 5 Equivalence of Energy: Heat, Electrical, Light 0. Pre-Laboratory Work [20 pts] As discussed in section 2.1, the speed of electrons entering an area of high resistance (like a bend in the wire, for instance) is higher before the bend and lower after it. From this, we might be inclined to think that the current is greater before the bend and lower after it. Why (after the current has been turned on for some time) can't this be true? Hint: one way to answer this is to think about what it would mean for the structural integrity of the wire if the current entering part of the wire was much greater than the current leaving that part. [10 pts] 1. 2. In the circuit you build in this lab it is very important that the power not exceed 35 W in the lightbulb, otherwise you may destroy it. Let's say that during the experiment you look at your multimeters and see that there is a voltage drop V 14 V across the lightbulb and current I 3 A running through it. a) How much power, P, is going into the lightbulb? [5 pts] b) Does the power exceed the 35 W it is safe to send into the lightbulb? [5 pts]

Explanation / Answer

1)we know that,

V = IR => I = V/R

for a given supply the voltage remains same and for a given wire even the value of resistance remains same, so the current will also be same irrespectibe of the geometry of the wires where its been flowing.

We know that the speed of the electrons in a wire(drift speed) is related to current as

Vd = I/n e A

for a wire n and A remains constant, unless a special case.

In a bent, A might have reduced and hence, the velocity became higher, but there would be no change of current.

2)Given,

P = 35 W ; V = 14 V ; I = 3 A

a)We know that

P = V I

P = 14 x 3 = 42 W

b)Yes it is exceeding 35 W, no it is not safe, as the bulb will get shot or destroyed.

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.