
Concept explainers
(a)
The sign of the charge of the ions.
(a)

Answer to Problem 94P
The sign of the charge of the ions is positive .
Explanation of Solution
The right hand rule states that in the case of a cross product, if the index finger of the right hand points in the direction of the first vector and the second vector points in the direction of the thumb, then the cross product will point in the direction of the thumb. Magnetic Lorentz force on a moving charge is the product of the charge and the cross product of the velocity of the charge and the magnetic field.
Right hand rule for the Lorentz force can be described as if the index finger of the right hand points in the direction of velocity of charge, the middle finger in the direction of the magnetic field, then the thumb will point in the direction of the magnetic force. In the given diagram, the velocity is directed to right, the magnetic field is directed into the page and the force is directed upward. This implies the ion is positive.
(b)
The accelerating plate which is positively charged.
(b)

Answer to Problem 94P
The positively charged accelerating plate is west plate .
Explanation of Solution
In part (a), it is found that the ions are positively charged. Positive ions will be attracted by negatively charged plates and will be repelled by positively charged plates. In the given diagram, the ions are accelerated towards the right.
Since the ions are accelerated towards right, the east plate must be negatively charged. This implies the other accelerating plate must be positively charged. Thus the west plate is positively charged.
(c)
The deflection plate which is positively charged.
(c)

Answer to Problem 94P
The positively charged deflection plate is north plate .
Explanation of Solution
Right hand rule for the Lorentz force can be described as if the index finger of the right hand points in the direction of velocity of charge, the middle finger in the direction of the magnetic field, then the thumb will point in the direction of the magnetic force. In a mass spectrometer, the correct velocity is selected by making the net force which is the sum of electric and magnetic force on the charge to be zero.
According to the right hand rule, the magnetic force on the positively charged ions is northward between the deflecting plates. To make the net force zero to select the correct velocity, the electric field must be southward. Since electric field points from positive plate to the negative plate, the north plate must be positively charged.
(d)
The correct values of ΔV1 and ΔV2 in order to count 12C+ ions.
(d)

Answer to Problem 94P
The value of ΔV1 to count 12C+ ions is 1.6 kV and that of ΔV2 is 320 V .
Explanation of Solution
Write the equation for the magnetic Lorentz force.
→F=q(→v×B)=qvBsinθ
Here, →F is the magnetic Lorentz force, q is the charge of the ion, v is the velocity of the ion, B is the magnetic field and θ is the angle between velocity and the magnetic field
The angle between the magnetic field and the velocity is 90° .
Substitute 90° for θ in the above equation.
→F=qvBsin90°=qvB (I)
The magnetic Lorentz force provides the centripetal acceleration required for the semi-circular motion of the ions.
Write the equation for the centripetal force.
→Fc=mv2r (II)
Here, →Fc is the centripetal force, m is the mass of the ion and r is the radius of the path
Equate equations (I) and (II) and rewrite the equation for v .
qvB=mv2rv=qrBm (III)
Write the equation for a velocity selector.
E=vB
Here, E is the magnitude of the electric field
Put equation (III) in the above equation.
E=(qrBm)B=qrB2m (IV)
Write the equation for the potential difference across the deflecting plates.
ΔV2=Ed
Here, ΔV2 is the potential difference across the deflecting plates and d is the separation between the plates
Put equation (IV) in the above equation.
ΔV2=(qrB2m)d=qrB2dm (V)
Apply the principle of conservation of energy for the given situation.
12mv2=qΔV1
Here, ΔV1 is the potential difference between the charged accelerating plates
Rewrite the above equation for ΔV1 .
ΔV1=mv22q
Put equation (III) in the above equation.
ΔV1=m2q(qrBm)2=qr2B22m (VI)
Conclusion:
Given that the radius of the path is 0.10 m , the value of the magnetic field is 0.20 T and the separation between the deflection plates is 1.00 cm . The charge of the ion is 1.60×10−19 C and the mass of the 12C+ ions is 1.993×10−26 kg .
Substitute 1.60×10−19 C for q , 0.10 m for r , 0.20 T for B , 1.00 cm for d and 1.993×10−26 kg for m in equation (V) to find ΔV2 .
ΔV2=(1.60×10−19 C)(0.10 m)(0.20 T)2(1.00 cm(1 m100 cm))1.993×10−26 kg=(1.60×10−19 C)(0.10 m)(0.20 T)2(0.010 m)1.993×10−26 kg=320 V
Substitute 1.60×10−19 C for q , 0.10 m for r , 0.20 T for B and 1.993×10−26 kg for m in equation (VI) to find ΔV1 .
ΔV1=(1.60×10−19 C)(0.10 m)2(0.20 T)22(1.993×10−26 kg)=(1.60×10−19 C)(0.10 m)2(0.20 T)22(1.993×10−26 kg)=1.6×103 V=1.6 kV
Therefore, the value of ΔV1 to count 12C+ ions is 1.6 kV and that of ΔV2 is 320 V .
(e)
The correct values of ΔV1 and ΔV2 in order to count 14C+ ions.
(e)

Answer to Problem 94P
The value of ΔV1 to count 14C+ ions is 1.4 kV and that of ΔV2 is 280 V .
Explanation of Solution
Equation (VI) and (V) respectively can be used to determine ΔV1 and ΔV2 with the mass of 14C+ ions.
Conclusion:
Given that the mass of the 14C+ ions is 2.325×10−26 kg .
Substitute 1.60×10−19 C for q , 0.10 m for r , 0.20 T for B and 2.325×10−26 kg for m in equation (VI) to find ΔV1 .
ΔV1=(1.60×10−19 C)(0.10 m)2(0.20 T)22(2.325×10−26 kg)=(1.60×10−19 C)(0.10 m)2(0.20 T)22(2.325×10−26 kg)=1.4×103 V=1.4 kV
Substitute 1.60×10−19 C for q , 0.10 m for r , 0.20 T for B , 1.00 cm for d and 2.325×10−26 kg for m in equation (V) to find ΔV2 .
ΔV2=(1.60×10−19 C)(0.10 m)(0.20 T)2(1.00 cm(1 m100 cm))2.325×10−26 kg=(1.60×10−19 C)(0.10 m)(0.20 T)2(0.010 m)2.325×10−26 kg=280 V
Therefore, the value of ΔV1 to count 14C+ ions is 1.4 kV and that of ΔV2 is 280 V .
Want to see more full solutions like this?
Chapter 19 Solutions
Physics
- (a) For a spherical capacitor with inner radius a and outer radius b, we have the following for the capacitance. ab C = k₂(b- a) 0.0695 m 0.145 m (8.99 × 10º N · m²/c²)( [0.145 m- 0.0695 m × 10-11 F = PF IIarrow_forwardA pendulum bob A (0.5 kg) is given an initialspeed of vA = 4 m/s when the chord ishorizontal. It then hits a stationary block B (1kg) which then slides to a maximum distanced before it stops. Determine the value of d.The coefficient of static friction between theblock and the plane is μk = 0.2. The coefficientof restitution between A and B is e = 0.8.Ans: d=1.0034 marrow_forwardFigure 29-43 Problem 12. ••13 In Fig. 29-44, point P₁ is at distance R = 13.1 cm on the perpendicular bisector of a straight wire of length L = 18.0 cm carrying current i = 58.2 mA. (Note that the wire is not long.) What is the magnitude of the magnetic field at P₁ due to i? P2° R R Larrow_forward
- Checkpoint 1 The figure shows the current i in a single-loop circuit with a battery B and a resistance R (and wires of neg- ligible resistance). (a) Should the emf arrow at B be drawn pointing leftward or rightward? At points a, B C R b, and c, rank (b) the magnitude of the current, (c) the electric potential, and (d) the electric potential energy of the charge carriers, greatest first.arrow_forwardPls help ASAParrow_forwardPls help asaparrow_forward
- Pls help asaparrow_forward3. If the force of gravity stopped acting on the planets in our solar system, what would happen? a) They would spiral slowly towards the sun. b) They would continue in straight lines tangent to their orbits. c) They would continue to orbit the sun. d) They would fly straight away from the sun. e) They would spiral slowly away from the sun. 4. 1 The free-body diagram of a wagon being pulled along a horizontal surface is best represented by A F N B C 0 Ꭰ FN E a) A b) B c) C app app The app 10 app d) e) ס ח D E 10 apparrow_forwardPls help ASAParrow_forward
- College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningUniversity Physics (14th Edition)PhysicsISBN:9780133969290Author:Hugh D. Young, Roger A. FreedmanPublisher:PEARSONIntroduction To Quantum MechanicsPhysicsISBN:9781107189638Author:Griffiths, David J., Schroeter, Darrell F.Publisher:Cambridge University Press
- Physics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningLecture- Tutorials for Introductory AstronomyPhysicsISBN:9780321820464Author:Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina BrissendenPublisher:Addison-WesleyCollege Physics: A Strategic Approach (4th Editio...PhysicsISBN:9780134609034Author:Randall D. Knight (Professor Emeritus), Brian Jones, Stuart FieldPublisher:PEARSON





