Heather C

It's someone I've never seen in real life, but he keeps showing up in my dreams as a menacing yet somehow comforting presence.

So I was trying to set up my wireless internet myself. Internet works, everything works--except every time I turn on the computer I get a message saying I need to reinstall from the disc, due to some router error (I also couldn't eject the disc because it said it was in use, but I eventually got it out).

Anything I can do about this mysterious error message? I really don't want to have to pay for a technician to come fix it.

I am using a macbook running osX Leopard if that helps.

I've been mixing baking soda and powdered sugar and leaving it out (the ants are supposed to eat the baking soda by mistake and explode). Is the baking soda safe for my cat? Are there any other ways to get rid of ants?

I really like Joy of Cooking, and have gotten lots of use out of it (it's what I use almost exclusively when making pie), but my absolute favorite is the American International Encyclopedic Cookbook. It's out of print, ancient (from the 1970s), and completely indispensable. I'm constantly referring to it when trying out new techniques. One of its best features is the way it lists a master recipe, followed by all kinds of variations--perfect for learning.

Light rays from a distant point source are incident perpendicular to the flat side of a semicircular glass plate of radius 5.8 cm and index 1.5. Find the distance of the image from the center of the curved side.

A certain microwave oven produces microwaves of frequency 2450 MHz with a power of 500 W. How long should it take to heat 477 g of water, initially at room temperature, to the boiling point? Assume that all the microwave energy is absorbed by the water. (The microwave frequency is significant because the water molecule has a rotational resonant frequency at 2450 MHz. This means that water very effectively absorbs radiant energy at this frequency, thereby raising its rotational kinetic energy and its temperature. The specific heat of water is 4186 J/kg–C°, and assume that the room temperature is 20°C.)

TV channel 2 broadcasts in the frequency range 51 to 59 MHz. What is the corresponding range of wavelengths? (Let us denote the minimum and maximum wavelengths by λmin and λmax, respectively.)

A long, straight wire lies along the y-axis and carries a current of 9.5 A in the positive y direction. A second long, straight wire, parallel to the first and 9.8 cm to the right, carries a current of 5.40 A in the negative y direction. At what value of the x coordinate does the resultant magnetic field vanish?

An aluminum wire has the same resistance as a copper wire of the same length. Find the ratio of the aluminum wire's diameter to the copper wire's diameter. (The resistivities of aluminum and copper are 2.82 *10^-8 Ω-m and 1.72 * 10^-8 Ω-m, respectively.)

Car batteries are often rated in amp-hours. This rating indicates the quantity of charge that can pass through the battery before the battery's chemical energy must be restored by the car's generator or some other source. The amp-hour unit is convenient for simple calculations. For example, a 60-amp-hour battery can supply a current of 1.0 A for 60 h (or 60 A for 1.0 h) before going dead. Find the energy stored in the following.

(a) a 54 A-h, 10 V car battery

(b) a 1.1 A-h, 1.4 V flashlight battery

A capacitor is not the most efficient device for storing energy. Batteries can store more energy in much less space. For example, a typical 12 V automobile battery stores on the order of 1.00 * 10^6 J.

(a) Find the capacitance necessary to store 1.00 *10^6 J with a potential difference of 1.00 *10^4 V across the capacitor's terminals.

(b) Suppose that such a capacitor was made in the form of a parallel-plate capacitor with a vacuum between the plates and an electric field no greater than 7.00* 10^6 V/m. What is the minimum area of the plates?

When a car's starter is in use, it draws a large current. The car's lights draw much less current. As a certain car is starting, the current through the battery is 66.0 A and the potential difference across the battery terminals is 8.91 V. When only the car's lights are used, the current through the battery is 1.98 A and the terminal potential difference is 12.1 V. Find the battery's emf and internal resistance.

When a car's starter is in use, it draws a large current. The car's lights draw much less current. As a certain car is starting, the current through the battery is 66.0 A and the potential difference across the battery terminals is 8.91 V. When only the car's lights are used, the current through the battery is 1.98 A and the terminal potential difference is 12.1 V. Find the battery's emf and internal resistance.

The terminal voltage of a certain battery is measured with the battery disconnected and is found to be 5.64 V. The internal resistance of the battery is 1.07 Ω. Find the voltage across the battery terminals when there is a current of 2.06 A from the negative to the positive terminal.

A capacitor is not the most efficient device for storing energy. Batteries can store more energy in much less space. For example, a typical 12 V automobile battery stores on the order of 1.00 * 10^6 J.

(a) Find the capacitance necessary to store 1.00 *10^6 J with a potential difference of 1.00 *10^4 V across the capacitor's terminals.

(b) Suppose that such a capacitor was made in the form of a parallel-plate capacitor with a vacuum between the plates and an electric field no greater than 7.00* 10^6 V/m. What is the minimum area of the plates?

The plates of a parallel-plate capacitor each have an area of 0.1 m^2 and are separated by a 0.6 mm thick layer of paper. The capacitor is connected to a 10 V battery. (The dielectric constant for paper is 4.)

(a) Find the capacitance.

(b) Find the charge stored.

A capacitor has parallel plates that have an area of 0.92 cm2 and are 1.08 mm apart. There is a vacuum between the plates, and the electric field magnitude is 9.00 105 N/C.

(a) Find the potential across the plates.

(b) Find the charge.

I got the first part correct (972V) but can't figure out how to get the right answer for the second part.

A certain resistor is made with a 48.8 m length of fine copper wire, 4.80 10-2 mm in diameter, wound onto a cylindrical form and having a fiber insulator separating the coils. Calculate the resistance. (The resistivity of copper is 1.72 10-8 Ω-m.)

A certain electric extension cord has a resistance of 5.92 Ω. Suppose it is replaced by an extension cord made of the same material. The replacement cord is five times the diameter of the original and five times as long. What is the resistance of the new cord?

(a) Find the equivalent capacitance when two 8 µF capacitors are connected in parallel.

(b) Find the equivalent capacitance when two 8 µF capacitors are connected in series.