1. The risk of electric shock depends entirely on the current passing through the human body. ( )

2. When a conductor moves in a magnetic field, there is always an induced potential in the conductor. ( )

3. The greater the wattage of incandescent light bulb, the smaller its resistance. ( )

4. The grounding distance of low-voltage household connecting wires should not be less than 2.5 meters. ( )

5. Outdoor vertical wires should be wrapped with insulation tape from bottom to top. ( )

6. The protection of the three-eye socket is connected to the zero-line pile head, and the lead wire should be directly connected to the zero-line pile head during wiring. ( )

7. When repairing metal containers such as boilers, 36V safety lights should be used for lighting. ( )

8. In the urban low-voltage public distribution network, the protection zero connection mode should not be adopted. ( )

Second, multiple-choice questions (fill in the correct answer code in brackets, 3 points for each question)

1. When receiving an order that seriously violates the rules and regulations of electrical safety work, you should ().

① Consider execution ② Partial execution ③ Refuse execution.

2. Determine the direction of the magnetic field generated by a straight conductor or coil by the current direction, and use ().

① Right-handed rule ② Left-handed rule ③ Right-handed spiral rule

3. If the current in the circuit increases to the rated value of the fuse, the fuse will be ().

① immediate integration; (2) fuse within1hour; ③ Not fused.

4. If each group of wires in the power distribution device is red, green and Huang San in turn, the phase difference is ().

①u、v、w ②w、u、v ③v、w、u

5. If COS φ = 0.8 and the apparent power is 100kva, the reactive power is ().

① 20kVA ② 80kVA ③ 60kVA

6. If the motor is started by Y-D, its starting current is full-voltage starting ().

①1√ 3 times ② 1/3 times ③3 times.

7.36v voltage line insulation resistance should be not less than ().

①0.036mω ②0.22 mω ③0.5 mω

8. When the electrical fire must be put out after the electrical fire, () should be used.

① Fire water injection ② Carbon tetrachloride fire extinguisher ③ foam extinguisher.

Three. Fill in the blanks (4 points for each question)

1. In China, the high and low voltage of alternating current is divided by _ _ _ V or relative ground voltage _ _ V. Generally, _ _ V is called safe voltage, while _ _ V is called absolute safe voltage.

2. The choice of fuse should meet the requirements of reliability and selectivity. Among them, reliability refers to _ _ _ _ _ that should be able to pass normally and avoid the motor for a long time; Selectivity means that all levels of fuses should be _ _ _ _, and the fuses at the previous level (near the power supply side) are more than those at the latter level.

3. Serious motor overcurrent will cause _ _ _ _ _, which is generally due to _ _ _ _ _ of external load, _ _ _ _ _ of grid voltage or _ _ _ _ of motor power supply.

4. When operating the circuit breaker, it is forbidden to _ _ _ switch the knife. When cutting off the power supply, you should pull _ _ _ first, then _ _ _ _ _; When closed, the sequence is _ _ _ _.

5. Electricians should wear _ _ _ _ when entering the aerial work site; It is forbidden to _ _ _ _ transfer objects when working on the pole; Around the live equipment, are not allowed to use _ _ _ to measure; When using a ladder, be sure to _ _ _ _.

4. Question and answer (8 points for each question)

1. In the four circuits shown below, if the voltages of AC power supply and DC power supply are equal, and the inductive reactance is equal to the capacitive reactance. Try to distinguish the brightness of each electric light. ) and the power factor (or its range) of each circuit.

2. How to choose the melt of various loads such as electric lamp, electric heating, single motor and multi-motor?

3. Why is the secondary side of the current transformer in use not allowed to open? What should I do when I need to connect or disconnect wires?

4. What are the safety measures for power outage maintenance of electrical equipment? What should I check before sending power after maintenance?

5. What are the three basic measures of cardiopulmonary resuscitation? Write the essentials of mouth-to-mouth artificial respiration and chest compressions.

V. Additional Questions (Reference)

1. Try to analyze whether the ohm's law is applicable when the circuit is short-circuited or open-circuited: r = 0 when short-circuited and I = 0； when open-circuited; According to ohm's law, the formula U = IR always gets u=0v. Is this the right result? Why?

2. What are the five kinds of line working tickets? What is the safe distance between the straddle frame and railways, highways and power lines?