| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.34 |
| Score | 0% | 67% |
Which of the following will increase the magnetic field produced by the electric current in a wire?
construct the wire from insulative material |
|
wind the wire into a coil |
|
wrap the wire around a ceramic core |
|
construct the wire from conductive material |
A moving electric current produces a magnetic field proportional to the amount of current flow. This magnetic field can be made stronger by winding the wire into a coil and further enhanced if done around an iron containing (ferrous) core.
Inductance is a factor in which of the following?
determining energy stored by a capacitor |
|
a DC circuit |
|
batteries connected in serial |
|
an AC circuit |
Inductance is a property of an AC circuit (or a component in an AC circuit) that quantifies resistance to changes in current. The current in an AC circuit is continuously changing and inductive reactance (the opposition to change) depends both on the inductance of the circuit or component and the rate at which the current is changing.
Silver and gold are among the most highly conductive elements. Why is copper used much more often as a conductor in electrical circuits?
silver and gold are brittle |
|
silver and gold are costly |
|
copper is durable and relatively cheap |
|
all of these |
All conductors have resistance and the amount of resistance varies with the element. But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.
This circuit component symbol represents a(n):
DC source |
|
transformer |
|
transistor |
|
AC source |
In contrast to the constant one-way flow of direct current, alternating current changes direction many times each second. Electricity is delivered from power stations to customers as AC because it provides a more efficient way to transport electricity over long distances.
Which of the following statements about a capacitor is false?
it is safe to touch a capacitor with your hands as long as it is small |
|
to discharge a capacitor safely, use a high-wattage resistor comparable to the capacitance of the capacitor |
|
a capacitor remains charged even after the input voltage is removed |
|
you should always discharge any capacitors before working on an electronic circuit |
The purpose of a capacitor is to retain electric charge and it will do so even after its input voltage is removed. After the input voltage is removed, the capacitor will slowly discharge but, depending on the size and characteristics of the capacitor, discharging could take from a few minutes to a few years. So, it's never safe to touch a capacitor with your hands and you should make sure to discharge any capacitors in a circuit before working on it using an appropriately high-wattage resistor or a capacitor discharge tool.