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* BIO Calcium ion synapse transfer Children have about
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- Four point charges each haring charge Q are located at the corners of a square haring sides of length a. Find symbolic expressions for (a) the total electric potential at the center of the square due to the four charges and (b) the work required to bring a fifth charge q from infinity to the center of the square.arrow_forwardAn anxious physicist worries that the two metal shelves of a wood frame bookcase might obtain a high voltage if charged by static electricity,, perhaps produced by friction, (a) What is the capacitance of the empty shelves if they have area 1.00102m2 and are 0.200 m apart? (b) What is the voltage between them if opposite charges of magnitude 2.00 nC are placed on them? (c) To show that this voltage poses a small hazard, calculate the energy stored, (d) The actual shelves have an area 100 times smaller than these hypothetical shelves. Are his fears justified?arrow_forwardNerve cells in the human body and in other animals are modeled as very long cylindrical capacitors. Portions of some nerves are covered with a layer of fat known as myelin, which functions as the dielectric ( = 7) between two plates in the cylindrical capacitor model. The potential difference between the inner and outer walls of myelin in resting nerve cells is roughly Vinner Vouter = 70 mV. Find the linear charge density on the inner (positive) plate. Hint: Use the result of Example 27.8.arrow_forward
- Electronic flash units for cameras contain a capacitor for storing the energy used to produce the flash. In one such unit the flash lasts for 1/675 fraction of a second with an average light power output of 270 kW. (a) If the conversion of electrical energy to light is 95% efficient (because the rest of the energy goes to thermal energy), how much energy must be stored in the capacitor for one flash? (b) The capacitor has a potential difference between its plates of 125 V when the stored energy equals the value stored in part (a). What is the capacitance?arrow_forward(a) How much charge can be placed on a capacitor with air between the plates before it breaks down if the area of each plate is 5.00 cm2? (b) Find the maximum charge if polystyrene is used between the plates instead of air. Assume the dielectric strength of air is 3.00 106 V/m and that of polystyrene is 24.0 106 V/m.arrow_forwardYou are working at an electronics fabrication shop. Your current project is on the team producing capacitors for the timer circuit that delays the closing of an elevator door. According to its design specification, the timer circuit is to have a capacitance of 32.0 F between two points A and B. As sour capacitors come off the assembly line, you find that they have a variation of 5.00% from this value. After a team meeting to evaluate this situation, the team decides that capacitances in the range 32.0 0.5 F are acceptable and do not need modification. For capacitances outside this range, the director does not wish to discard the capacitors, but rather to add extra capacitors in series or parallel with the main capacitor to bring the total equivalent capacitance to the exact design value of 32.0 F. You are put in charge of procuring the extra capacitors. What range of capacitances for these extra capacitors do you need to cover the entire range of variation of 5.00%? All capacitances can be measured to three significant figures.arrow_forward
- a parallel-plate capacitor with area 0.200 m2 and plate separation of 3.00 mm is connected to a 6.00-V battery. (a) What is the capacitance? (b) How much charge is stored on the plates? (c) What is the electric field between the plates? (d) Find the magnitude of the charge density on each plate. (e) Without disconnecting the battery, the plates are moved farther apart. Qualitatively, what happens to each of the previous answers?arrow_forwardIn Figure 20. 1, two points and are located within a region in which there is an electric field. (i) How would you describe the potential difference V = V V? (a) It is positive. (b) It is negative. (c) It is zero. (ii) A negative charge is placed at and then moved to . How would you describe the change in potential energy of the chargefield system for this process? Choose from the same possibilities. Figure 20.1 (Quick Quiz 20.1) Two points in an electric field.arrow_forwardA supermarket sells rolls of aluminum foil, plastic wrap, and waxed paper. (a) Describe a capacitor made from such materials. Compute order-of-magnitude estimates for (b) its capacitance and (c) its breakdown voltage.arrow_forward
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