Foundations of Astronomy, Enhanced
13th Edition
ISBN: 9781305980686
Author: Michael A. Seeds; Dana Backman
Publisher: Cengage Learning US
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Chapter 18, Problem 17RQ
In which model universe does the average density of the Universe equal the critical density?
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4.) The diagram shows the electric field lines of a positively charged conducting sphere of
radius R and charge Q.
A
B
Points A and B are located on the same field line.
A proton is placed at A and released from rest. The magnitude of the work done by the electric field in
moving the proton from A to B is 1.7×10-16 J. Point A is at a distance of 5.0×10-2m from the centre of
the sphere. Point B is at a distance of 1.0×10-1 m from the centre of the sphere.
(a) Explain why the electric potential decreases from A to B. [2]
(b) Draw, on the axes, the variation of electric potential V with distance r from the centre of the
sphere.
R
[2]
(c(i)) Calculate the electric potential difference between points A and B. [1]
(c(ii)) Determine the charge Q of the sphere. [2]
(d) The concept of potential is also used in the context of gravitational fields. Suggest why scientists
developed a common terminology to describe different types of fields. [1]
3.) The graph shows how current I varies with potential difference V across a component X.
904
80-
70-
60-
50-
I/MA
40-
30-
20-
10-
0+
0
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VIV
Component X and a cell of negligible internal resistance are placed in a circuit.
A variable resistor R is connected in series with component X. The ammeter reads 20mA.
4.0V
4.0V
Component X and the cell are now placed in a potential divider circuit.
(a) Outline why component X is considered non-ohmic. [1]
(b(i)) Determine the resistance of the variable resistor. [3]
(b(ii)) Calculate the power dissipated in the circuit. [1]
(c(i)) State the range of current that the ammeter can measure as the slider S of the potential divider
is moved from Q to P. [1]
(c(ii)) Describe, by reference to your answer for (c)(i), the advantage of the potential divider
arrangement over the arrangement in (b).
1.) Two long parallel current-carrying wires P and Q are separated by 0.10 m. The current in wire P is 5.0 A.
The magnetic force on a length of 0.50 m of wire P due to the current in wire Q is 2.0 × 10-s N.
(a) State and explain the magnitude of the force on a length of 0.50 m of wire Q due to the current in P. [2]
(b) Calculate the current in wire Q. [2]
(c) Another current-carrying wire R is placed parallel to wires P and Q and halfway between them as shown.
wire P
wire R
wire Q
0.05 m
0.05 m
The net magnetic force on wire Q is now zero.
(c.i) State the direction of the current in R, relative to the current in P.[1]
(c.ii) Deduce the current in R. [2]
Chapter 18 Solutions
Foundations of Astronomy, Enhanced
Ch. 18 - Is cosmology the study of the Universe, the...Ch. 18 - Is a cosmologist an astronomer? Is an astronomer a...Ch. 18 - How does the darkness of the night sky tell you...Ch. 18 - Explain the differences among the observable...Ch. 18 - Prob. 5RQCh. 18 - Prob. 6RQCh. 18 - Prob. 7RQCh. 18 - Prob. 8RQCh. 18 - Prob. 9RQCh. 18 - Prob. 10RQ
Ch. 18 - Prob. 11RQCh. 18 - If you accept the cosmological principle, how can...Ch. 18 - Why cant an open universe have a center? How can a...Ch. 18 - In which type of model universe is space-time...Ch. 18 - In which type of model universe is space-time...Ch. 18 - What is the fate of a closed universe? In what...Ch. 18 - In which model universe does the average density...Ch. 18 - Prob. 18RQCh. 18 - What evidence shows that the Universe is...Ch. 18 - Why couldnt atomic nuclei exist when the Universe...Ch. 18 - Why are measurements of the current density of the...Ch. 18 - What percentage of matter is ordinary matter? What...Ch. 18 - How does the inflationary universe hypothesis...Ch. 18 - Prob. 24RQCh. 18 - What is the evidence that the Universe was...Ch. 18 - Prob. 26RQCh. 18 - If the Universe is negatively curved, and dark...Ch. 18 - What is the difference between hot dark matter and...Ch. 18 - Prob. 29RQCh. 18 - What evidence can you cite that the Universe's...Ch. 18 - Prob. 31RQCh. 18 - Reasoning by analogy often helps make complicated...Ch. 18 - Prob. 33RQCh. 18 - Prob. 1DQCh. 18 - Prob. 2DQCh. 18 - Prob. 3DQCh. 18 - Prob. 1PCh. 18 - Prob. 2PCh. 18 - Prob. 3PCh. 18 - Measure the lengths of the two arrows in the left...Ch. 18 - Prob. 5PCh. 18 - Prob. 6PCh. 18 - Find the wavelength of maximum intensity of the...Ch. 18 - Prob. 8PCh. 18 - Prob. 9PCh. 18 - Prob. 10PCh. 18 - Prob. 11PCh. 18 - Prob. 12PCh. 18 - Prob. 1LTLCh. 18 - Prob. 2LTLCh. 18 - Prob. 3LTLCh. 18 - Prob. 4LTLCh. 18 - Prob. 5LTLCh. 18 - Prob. 6LTL
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