ELEX Pre-Board Exam 12

An advantage of an electromagnet over a permanent magnet is that:

• An electromagnet can be switched on and off
• An electromagnet does not have specific polarity
• An electromagnet requires no power source
• Permanent magnets must always be cylindrical

The quantity of magnetism retained by a magnetic material after withdrawal of the magnetized force is called

• Leftover magnetism
• Residual magnetism
• Hysteresis
• Coercivity

Three resistors of 10, 15, and 20 Ω each are connected in parallel. What is the total conductance?

• 0.217 S
• 3.41 S
• 4.62 S
• 0.52 S

What temperature in which the specific resistance of materials is usually measured?

• 290 K
• 300 K
• 20°C
• 0°C

When one resistance in a series string is open, the

• current is maximum in the normal resistances
• current is zero in all of the resistances
• voltage is zero across the open resistance
• current increases in the voltage source

The equivalent wye element of 3 equal resistors each equal to R and connected in delta is

• R
• 3R/2
• R/3
• 3R

A lead storage battery is rated at 12 V. If the internal resistance is 0.01 Ω, what is the maximum power that can be delivered to the load?

• 1,200 W
• 7,200 W
• 3,600 W
• 1,800 W

A simple circuit having a source of 7 nanovolts and a load of 3 kilo-mega ohms has a current equivalent to

• 23.33 amperes
• 2.333 attoamperes
• 2.333 amperes
• 2.333 deca amperes

What happens to the flow of electrons in electronic circuit when the resistance is increased?

• The speed of flow will remain constant
• The flow become faster
• The flow will be decreased
• No flow will occur

A circuit contains an inductor of 10 H in series with the capacitor of 0.001 F and operating at a frequency of 4 MHz. What is the net reactance or X in MΩ?

• 2.4727
• 2472.7
• 247.27
• 24.727