Physics Electrostatics Level: High School
An air-filled parallel-plate capacitor has a capacitance of 1.4 pF. The separation of the plates is doubled and wax is inserted between them . The new capacitance is 2.4 pF. Find the dielectric constant of the wax
Physics Electrostatics Level: High School
A 2.9 micro F capacitor and a 4.4 micro F capacitor are connected in parallel across a 330 V potential difference . Calculate the total energy in joules stored in the capacitors .
Physics Electrostatics Level: High School
Hydrogen atom is a single electron revolves around a single proton in a circle of radius r, assume proton is at resta) by equating the electrical force to the electron mass times is acceleration, derive an expression for the electrons speed .
b) Obtain an expression for the electrons kinetic energy and show that its magnitude is just half of the electrical potential energy .
c) Obtain an expression for the total energy and evaluate it using r = 5.29*10^-11m . Give your numerical results in Joules and electron volts .
Physics Electrostatics Level: High School
A potential difference of 800 V is established between two parallel plates 3cm apart an electron is released from the negative plate at the same instant a proton is released from the positive plate .a) How far from the positive plate will they pass each other ?
b) What is the ratio of their speeds when they strike the opposite plate ?
c) What is the ratio of their kinetic energies when they strike the opposite plates ?
Physics Electrostatics Level: High School
Some cell walls in the human body have a double layer of surface charge with a layer of negative charge inside and a layer of positive charge of equal magnitude on the other. Consider a model for such a cell in which surface charge densities are + or – 5*10^-3 and the cell wall is 5.0*10^-9 m thick (Note use using parallel plates)a) Find the electric field magnitude in the wall between the two charge layers
b) The potential difference between inside and outside the cell . Which is the higher potential.
Physics Electrostatics Level: High School
A positive charge +q is located at the point (x = 0, y = -a) and an equal charge –q is located at point (x = 0, y = +a)a) Draw a diagram showing positions of the charges.
b) What is the potential at a point on the x axis distance x from origin .
c) Derive an expression for the potential at a point on the y-axis a distance y from the origin.
d)sketch a graph of the potential at points on the y-axis as a function of y in the range of y = -4a to y = +4a . Plot positive potentials upward and negative potential downward .
Physics Electromagnetic Induction Level: High School
Step up transformer
A transformer charges 120 V across the primary to 1200 V across the secondary . If the secondary coil has 800 turns, how many turns does the primary coil have ?a) 40
b) 80
c) 100
d) 400
e) 4000
Physics Electromagnetic Induction Level: High School
Determine the energy stored in a 95-mH inductor that carries a 1.4-A current.a) 0.38 J
b) 0.27 J
c) 0.19 J
d) 0.093 J
e) 0.066 J
Physics Electromagnetic Induction Level: High School
The angular speed of a motor is 262 rad/s. The back emf generated by the motor is 89.4 V. Assuming all other factors remain the same, determine the back emf if the angular speed of the motor is reduced to 154 rad/s .a) 32.3 V
b) 44.7 V
c) 52.5 V
d) 89.4 V
e) 152 V
Physics Electromagnetic Induction Level: High School
A long straight wire in the same plane as a rectangular , conducting loop . The wire carries a constant current 1 as shown in the figure at “click here” . Which one of the following statements is true if the wire is suddenly moved toward the loop ?a) There will be no induced emf and no induced current.
b) There will be an induced emf, but no induced current.
c) There will be an induced current that is clockwise around the loop .
d) There will be an induced current that is counterclockwise around the loop.
e) There will be an induced electric field that is clock wise around the loop.
Physics Magnetism,Magnetic Effects Of Current Level: High School
Earth’s magnetism
The Earth’s magnetic field passes through a square tabletop with a magnitude of 4.95 x 10^-5 T and directed at an angle of 165 degree relative to the normal of the tabletop. If the tabletop has 1.50 –m sides , what is the magnitude of the magnetic flux through it ?a) 108 x 10^-4 Wb
b) 7.11 x 10^-5 Wb
c) 2.88 x 10^-5 Wb
d) 1.92 x 10^-5 Wb
e) 3.30 x 10^-6 Wb
Physics Electromagnetic Induction Level: High School
A conducting loop of wire is placed in a magnetic field that is normal to the plane of the loop . Which one of the following actions will not result in an induced current in the loop ?a) Rotate the loop about an axis that is parallel to the field and passes through the center of the loop .
b) Increase the strength of the magnetic field
c) Decrease the area of the loop
d) Decrease the strength of the magnetic field
e) Rotate the loop about an axis that is perpendicular to the field and passes through the center of the loop .
Physics Magnetism,Magnetic Effects Of Current Level: High School
Solenoid
Which one of the following material is not ferromagnetic ?a) Iron
b) Chromium dioxide
c) Nickel
d) Aluminum
e) Cobalt
Physics Magnetism,Magnetic Effects Of Current Level: High School
Solenoid
A solenoid of length 0.250 m and radius 0.0200 m is comprised of 120 turns of wire . Determine the magnitude of the magnetic field at the center of the solenoid when it carries a current of 15.0 Aa) 2.26 x 10^-3 T
b) 4.52 x 10^-3 T
c) 9.05 x 10^-3 T
d) 7.50 x 10^-3 T
e) zero tesla
Physics Magnetism,Magnetic Effects Of Current Level: High School
Force on a current carrying conduction
A current-carrying , rectangular coil of wire is placed in a magnetic field . The magnitude of the torque on the coil is not dependent upon which one of the following quantities ?a) The magnitude of the current in the loop
b) The direction of current in the loop
c) The length of the sides of the loop
d) The area of the loop
e) The orientation of the loop
